DailyTech reports testers of Windows Vista SP1 are getting mixed results. In some areas the SP1 does better but unfortunately it introduces problems in others:
One key question on Windows Vista users' minds is exactly how does Windows post SP1 measure up against the initial copy of Windows Vista in terms of performance. In initial testing at CNET Labs, the results are in, and they are rather mixed. Testers found that while SP1 improves performance under some condition, it actually decreases performance under others. For the most part, testers concluded, few will notice the difference between the base installation and an SP1 installed system.
Vista does offer bundled updated third party drivers which do upgrade performance significantly, but most of these were already available. Customers who have kept current with Window's Updates and their third party driver updates will find little new here, and thus will see no real performance change. Microsoft definitely can take credit in a big picture sense for providing improved performance, though, as it has been devoting considerable resources to helping third party vendors make their products better compatible with Windows, gradually improving performance over the last year.
Probably the single biggest changes in performance have to do with file copying. Windows XP used an cached I/O mode to improve write times. Windows Vista on the other hand used a slower predominately uncached I/O system. The upgrade to SP1 adds caching back into the mix, which in most cases, testers discovered, improves results.
On the other side of things, the SP1 update has somehow created a performance degradation in copy times to external USB 2.0 hard drives. Something is going wrong in Windows Vista SP1 during USB copies, and the issue is currently under investigation. Meanwhile Windows Vista SP1 takes a 40 to 50 percent performance hit in this type of file copies, when compared to base Windows Vista.