Microsoft's Windows Vista has accumulated a very large user base since its release to the public in January 2007.  The recently released SP1 included bundled drivers with the aim of increased compatibility in users' machines who do not regularly perform driver updates.  It also includes speed ups to hibernation recovery, and the ability to use encryption tool BitLocker on multiple drives. 

Furthermore, to improve hard drive write times, SP1 moved Vista from an uncached write system to a cached I/O mode system.  The net result was slight increases in hard drive write speeds, according to preliminary tests; though surprisingly, the test found that USB drive write speeds dropped significantly. 

SP1 shipped to English language volume customers, MSDN subscribers, and testers last month.  Initially, some users experienced a catastrophic failure when one of the previous Windows updates was found to trigger an endless boot loop after the installation of SP1.  Microsoft quickly pulled the offending update.  Now with the release of SP1 to the general public, the large test population is sure to reveal any flaws in the SP1 if there are any.

And it turns out there may be, if initial reports are to be believed.  Some people are still reporting being locked into the boot loop, possibly due to the lingering presence of the malignant update.  Many users left pointed remarks about the various failures on Microsoft's Vista Team's blog.  Some users remarked that the update destroyed the latest versions of their NVIDIA drivers.  Says commenter "SeppDietrich", "What a disaster-- It exiled all my NVIDIA drivers to the Bermuda Triangle."

Other users complained of significant slowdowns.  "After installing SP1 things seem to go really slow, even though my computer shouldn't have any problems," said one commenter named "Bikkja".

Part of the slowdown may be due to spiking memory demands experienced by some users.  One user "Kurrier" reported that his memory usage by the OS jumped from 650 MB to 1 GB.  He announced that he would definitely be switching back to the pre-SP1 version of Vista.

Also, SP1 would not install on some computers which have incompatible hardware drivers.   A small set of Intel and Realtek drivers are among those deemed incompatible.  For the full list of incompatible hardware, refer here.  Microsoft is working to resolve these issues.

One should note that service packs often wreak havoc on users’ computers and that Windows has a long history of releasing Service Packs that negatively affected some users.  Windows XP SP1, while delivering essential updates in 2002 caused many problems, which Microsoft scrambled to fix in a series of subsequent patches. 

Windows SP1 is currently available in five languages: English, French, German, Japanese, and Spanish.  Some retailers such as Amazon started selling boxed copies of the update yesterday.  Users must install prerequisite files before install Vista SP1, including the allegedly fixed prerequisite that caused the boot loop crash on some users' machines.