Apple's latest operating system effort, OS X 10.7 "Lion", was recently released in preview form to developers.  The operating system looks to be a major departure from past versions of OS X in several ways.  Most notably the entire OS is shifting to iOS' (iPad, iPhone) model of an experience built around an app store.  Even the applications launcher has become "more iOS-like".

Now some of the other new features -- finer details, so to speak, have begun to be discovered by the Mac enthusiast community.

I. New Features Galore

A major news item is the fate of OS X Lion Server has been spelled out.  Like Windows, Apple releases a server edition accompanying nearly every major release.  While there aren't a ton of Apple server customers, for those out there, they will be excited to know that Lion Server is built into the base OS X 10.7 Lion distribution and is entirely free.  This might tempt Mac enthusiasts to try to set up their own backup storage servers.

Apple describes:

Lion Server guides you through configuring your Mac as a server. And it provides local and remote administration — for users and groups, push notifications, file sharing, calendaring, mail, contacts, chat, Time Machine, VPN, web, and wiki services — all in one place. 

Apple has also dropped the PowerPC software support that is available in Snow Leopard via Rosetta.  The move is calculated plot to force users away from PowerPC entirely.

Another useful feature on the firmware level is the inclusion of "TRIM".  This feature only applies to users of solid-state drives.  Basically, it's an improvement to the SSD firmware that revamps garbage collection to prevent write speed degradation on blocks you previously wrote to.  The net result should be a bit snappier SSD performance over time.  Windows users can enjoy a snicker here as TRIM has long been supported in Windows.

Yet another relatively "big" improvement is to the popular "Time Machine" feature, which is somewhat akin to Windows Restore.  Previously the feature required an external hard drive to take recovery snapshots.  Now you can enable the feature to use your internal drive.  In this mode snapshots are taken nearly every hour.

The new feature goes hand in hand with "Versions" which acts something like an automatic skinned SVN client, saving copies of a document every time you make a change to it and displaying them, if you wish to revert a file to a previous point.

Another new feature is "Air Drop"; a little app that allows you to transfer files over wireless networks by a simple drag and drop interface.  It actually looks pretty slick -- you can auto-locate nearby users with Air Drop enabled.  Of course it also seems like a bit of a security risk.

Apple has added the ability for multiple users to be remotely logged in to a machine at once.  Previously if another account was logged into your remote OS X machine you could only enjoy a movie of what they were doing.  Now you can do that or log in in parallel via your account.

FaceTime HD also comes loaded in the developer build.  Essentially Apple's take on a Skype/chat service, the app features full 720p mode.  It isn't free; Apple will be charge exactly $1 in what is likely less a bid for direct revenue and more of a bid to get customers entered into the new Mac App Store system (if they haven't been already).

Another new app is Podcast Producer that was previously only available to "pro" paying server users.  The app is similar in nature to Garage Band and its ilk, allowing you to quickly and (relatively) easily create podcasts.

IChat has added support for Yahoo IM accounts.  And the client now offers hover-over previews for your convenience.  Another minor tweak is the inclusion of hover-over-to-play in iTunes’ album art screensaver mode.

Another handy new feature is "Signature Capture" a little app that lets you to write a signature (on paper) and then hold it up to the system's web cam.  A shot is then capture and interpreted into a filtered image file.  That image can be added to make your PDFs, etc. all official.

The latest version of the email client, Mail 5 has been revamped and looks much more iOS-like.  Support for Exchange 2010 is built in.

The new build also offers clues in its file system that points to a "Find My Mac" feature, similar to "Find My iPhone", being included in the final version of Lion.  This feature is not currently included, but the telltale signs are there.

In the mystery department, Front Row, Apple's media center, has disappeared from Developer builds, leading to speculation that Apple is working on a replacement product, possibly built-into iTunes.

Another minor change that has some OS X fans spooked is the change in the default settings of the scroll [video].  9 to 5 Mac describes the shift as leading to "a very difficult transition".  This again seems to get back to Apple's desire to make the OS more iOS-like.  Scrolling up moves the page up (moves your position down the page), just like it would on a smart phone or tablet.  Fortunately for those unwilling to change their ways, Apple has built in an option to revert this setting to Snow Leopards default (scrolling down to move position down/move the page up).

II. Downloading and Installing the Preview -- Requirements and More

After Apples announcement of the developer preview was made last week, the logistics of its distribution slowly trickled out.  It would be delivered via the Mac App Store with a redeemable code sent to developers.  For those who aren't OS X developers and aren't sure quite what an OS X "developer" is, it's a simple $99 once-yearly subscription fee that gives you access to previews and other goodies.  

Unsurprisingly, not everyone wanted to pay that fee and it took little time for the OS to hit torrents. (Beware, developers, the OS reports back to Apple at swcan.apple.com -- unless you block that domain you risk discovery and possibly getting booted from Apple's developer efforts.)

Speaking of crackdowns, Apple also has begun to issue copyright notices to try to take down OS X Lion videos on YouTube.  Though it may be a futile effort, Apple sure is trying.  Posting videos is a violation of your developer contract, so beware the wrath of Steve Jobs and company.

The OS has plenty of requirements/installation notes.  Among the highlights are:
- You must have a Core 2 Duo or better
- Installing to a software Raid configuration is not currently available and may render your volume unusable (wow, at least they warn you!)
- Lion Server (if you plan on installing it) must be installed on an empty disk
- You cannot be running an iMac (circa 2006 -- iMac support will likely be added for the final release)
- You must disable FileVault in Snow Leopard before upgrading to Lion.  Lion has replaced this feature with a new version of encryption software.
- Your volumes will not be readable by past versions of OS X
- If you plan on using Boot Camp, you need version 3.2 or later.

Primary Source: [source]

III.  Summary

To officially get Mac OS X Lion:
1.  Go here to sign up for a $99 Mac Developer account.
2.  Grab your redeem code for OS X Lion.
3.  Download it off the Mac App Store.

The new features in Lion, currently known or coming soon are:
+ Built in Lion Server support
+ TRIM SSD support
+ Launch Pad (app launcher)
+ Mission Control (app preview)
+ Remote multi-login
+ Versions, and local-disk Time Machine
+ Air Drop
+ FaceTime HD
+ Podcast Producer
+ Signature Capture
+ Front Row replacement
+ "Find My Mac" and dropbox storage -- coming soon in MobileMe
+ Yahoo Chat support
+ Revamped email client
+ Revised encryption (full disk XTS-AES 128, wow)

Notable missing features are:
+ Front Row (likely to be replaced)
+ PowerPC software support (will not be added)

While Windows users enjoy many a joke about Apple's frequent OS updates this release appears a bit bigger than Apple's average fare.  If nothing else it represents a major paradigm shift for Apple, moving away from a "traditional" PC operating system and trying to capture a bit of the app-driven fire from iOS.