Firefox 4.0 was supposed to release in November 2010.  Yet here it is, almost the end of March 2011, and the wayward browser has only now finally landed.  That delay allowed Microsoft's Internet Explorer 9 to hit the market before it. So was the four-month delay worth it?  Read on to find out.

I.  Stable, Feature Rich

In our basic testing we found that the late betas of Firefox 4 vastly improved the stability of the browser. When GPU acceleration was first dropped in at Beta 5, the build became very buggy and would crash every few minutes for us.  We diligently submitted our bug reports, but obviously we dropped the test build as our regular browser.

Unsurprisingly, the later builds were largely devoted to stomping out the many bugs that testers like us may have encountered.  The end result appears to be a very solid browser, which crashes less often the Chrome 10.  The latest build of Firefox 4.0 is still labeled as release candidate, but the version that will be released tomorrow will be identical.

We were unable to test and assess the stability in Linux and Mac OS X, but we would hope that the stability of the Windows build carries over to these releases.

The browser brings a host of goodies to the table.  One immediate change is a new user interface.  While it doesn't look that different, there are a number of new features.  

One feature we love is the country flag info icon.  With this icon you not only get a flag of where a particular site is hosted out of, but also its domain name and IP address.

Another useful change is the Firefox 4's decision to move extensions buttons into your main address bar.  While we could see this feature getting abused by foolish extensions developers, it can greatly improve the ease of using certain common extensions like NoScript, as you tend to mouse over this area more often than the bottom of the screen (where these buttons used to reside).

Another fun feature is tab grouping, which can be found by clicking the small drop arrow in the address bar, on the far right hand side of the screen.  While we feel tab grouping is clunkier than Opera's recent "tab stacking" innovation, it's still a useful organization tool to have in your arsenal.

Yet another likable change is the ability to turn websites into pinned "applications".  You can right click a tab to turn it into an application.  It shrinks down to the page icon and will always be present when you open your browser.

The handiness of this feature cannot be overstated.  If you have a handful of sites you regularly frequent -- say Gmail, Google Finance, and DailyTech -- this feature will save space on your tabs bar and be sure that you're always only a click away from your favorite sites.

Yet another slick feature is the fact that your program bar icon actually turns into a tiny downloads progress bar when you're downloading a file.  This may not seem terribly useful at first, but if you switch to a separate window during downloading a large file, this can turn from a cute touch into a valuable feature.

Support for multi-touch in Windows 7 has also been added, perhaps future-guarding for increased PC-side touch interfaces in years to come.

Last, but not least, there's the landing of GPU acceleration.  Firefox, Internet Explorer, and Chrome all support GPU acceleration in Windows now.  Opera is close to getting the feature and Apple's Safari surely be much farther behind.

II. Support For Windows XP

At the end of the day, one of the things that may give Firefox 4 its greatest boost in market share is a decision by Microsoft.  

Microsoft decided to only support the Windows Vista operating system and onward with the release of Internet Explorer 9.  Millions of home and business customers still use the Windows XP OS and were now blocked out of experiencing the latest and greatest innovations.

By contrast, Firefox 4 supports not only Windows XP, but also Windows 2000.  

Now there is some fine print.  While hardware (Direct3D) compositing will work in Windows XP, Direct2D rendering was not fully implemented, so you will only get partial GPU acceleration.  Of course most who would be worried about this probably wouldn't be running Windows XP anymore.

Could the support for Windows XP improve Mozilla's position in the business user market?  It's hard to say.  Internet Explorer is a much easier to manage from an IT perspective, as it was build largely with a large deployment in mind, where as Firefox was largely built for the individual user.  That means that past a small business, adopting Firefox may be a bit more challenging.

Still, the company could see some pickup due to Microsoft decision to ditch support for its own OS.

III. Standards and a Small Speed Test

We were still having issues with getting Internet Explorer 9 installing on our circa-2009 MacBook Pro with Windows 7 Premium and Boot Camp.  Namely, one of the prerequisite updates just wasn't working.  We had a 64-bit machine, but it was complaining that the update was not applicable.  We verified the authenticity of our version (which we already knew) and that it was indeed 64-bit via the msinfo32 tool in Windows 7.  We've submitted a bug report.

A brief look at forums shows us that we're not alone -- other users are also running into installation issues.  We said it in our IE9 review and we'll say it again here.  Microsoft needs a stand-alone installer.  This state of affairs is arguably unacceptable.  As a result of dependency issues, some users (like ourselves) can't get IE9 even installed.  And you thought Linux was annoying.

Due to that unfortunate event, we chose to pit Firefox 4.0 final exclusively against Chrome 10, the latest stable release of Google's browser.  Chrome is the second most popular third-party browser on the market after Mozilla's Firefox.

i. Standards

In The HTML5 Test we obtained the following results (higher is better):
1. Chrome 10 - 288 points (+13 bonus points)
2. Firefox 4.0 -- 240 (+8 bonus points)

Using Acid3, a general compatibility test, that tests things like CSS and SVG, we received:
1. Chrome 10 - 100/100
2. Firefox 4.0 -- 97/100

Verdict: 
Chrome 10 maintains a slight compatibility advantage over Firefox, though both browsers are quite good at supporting the latest web standards.

ii. Javascript

In the Sunspider Javascript test Firefox 4 ran faster, but did not properly animate the text, so we're not sure if we should call this a pass.  Nonetheless, here is the results (lower is better):
1.  Firefox 4.0 -- 299.1ms +/- 3.6%
2.  Chrome 10 - 509.7ms +/- 10.2%

We next ran Mozilla's own Kraken Javascript benchmark.  Note, in the fast we've noticed Firefox perform unusually well here versus third party benchmarks, so we tend to take its results with a grain of salt.  Here again, Firefox 4 didn't display text informing the user of the stage of the benchmark, so it was unclear whether it was fully running it properly.  Nonetheless, we obtained (lower is better):

1. Firefox 4.0 -- 8209.6ms +/- 1.6%
2. Chrome 10 - 10164.5ms +/- 1.8%

Next we ran Celtic Kane's JSBenchmark (higher is better).  The results, using 10 trials, are as follows:
1. Chrome 10 - 653 ± 80 
2. Firefox 4.0 -- 361 ± 21

Verdict:
In one independent test Chrome 10 took a clear lead.  In two other tests (including one from Mozilla) Firefox 4 was faster, but failed to render text properly (which may have had an impact on timings).  Thus we rule this roughly a incomplete verdict.  Both browsers look to be relatively fast, though, when it comes to Javascript.

iii. General Speed

To finish up, we ran the mother of all browser benchmarks, Peacekeeper.  Designed by Futuremark, this test measures performances of Javascript, CSS, SVG, and more.  We received (higher is better):
1. Chrome 10 - 8020 points
2. Firefox 4.0 -- 3511 points

Verdict:
Firefox still trails Chrome 10 in overall speed.  It was hard to reliably assess how the pair stack up in terms of Javascript performance, but it appears that they have a clear gap in terms of overall speed.  

This finding was consistent with qualitative examination, which showed pages like DailyTech loading noticeably faster, by appearance, in Chrome 10 than in Firefox 4.0.

IV. Final Words

Again Firefox 4.0's biggest weakness is that it's very late.  If it had debuted in its current form four months ago, it would have been a smash hit.  Instead it allowed Chrome to creep upwards in market share and Internet Explorer 9, amazingly, to beat it to market.

And Firefox's individual user design mindset means that it is less optimal for large-scale business installations than Internet Explorer 9.  And for home users, Chrome 10 is faster and supports more standards.

Still, Firefox 4 offers excellent extensions and a relatively slick and polished UI, both of which we enjoy.  And its support for Windows XP makes it one of the most appealing browsers for legacy users.

Firefox 4 won't necessarily catapult Mozilla ahead in market share, but it's also unlikely to lose the race for it.

The browser's installer is available here [Windows; here for Linux; here for OS X].  The webpage currently is still showing Firefox 3.6 and discussing the beta program for Firefox 4.  Expect this to be updated later today.

And check out Mozilla's Firefox 4.0 launch "parties".  It may sound corny, but Mozilla is taking a page out of Microsoft's book.  It might be more fun that you expect.