PC Magazine published an extensive and very interesting review on Microsoft Windows Vista Service Pack 1. Here's an excerpt:

The time Vista takes to return from hibernation mode has dropped markedly (by about half, in fact); it takes even less time with my clean install. Wake time was a major irritation when using Vista RTM, not only for laptop users (a fact Microsoft quickly recognized) but also, from my experience, when running the OS on desktops. With both the download install and the clean install of SP1, I no longer have time to make coffee after pushing the power button on my desktop PC to bring it out of hibernation. Better still, with drive access no longer constant, I can start work (or play) that much more quickly.  But actually, I no longer recommend hibernation as the best method for stopping your PC from eating power. By all accounts, sleep mode offers very nearly the same power savings, and coming out of it with SP1 takes only a few seconds. The update has also come a fair distance in correcting the problems RTM had with entering sleep or hibernate mode automatically (I typically had to resort to forcing my PC into those modes manually). On my download SP1 install, however, I still notice that, when running numerous programs, sleep sometimes doesn't initiate automatically. It does on my clean install, so obviously I have something installed and running on the download install that's blocking sleep/hibernate entry.

The speed of other day-to-day tasks has improved as well. Opening Windows Explorer for the first time in a session (which on my desktop took at least a full 30 seconds, and as long as a full minute) now takes an acceptable 10 to 15 seconds even on a system fully stocked with software, and only 3 to 4 seconds on my clean installation. Microsoft also boasts about speed improvements in Internet Explorer 7, both in its ability to work with JScript and its reading and loading of large images. I found no proof of the former, but I can say that spending a couple of hours on sites that offered high-res images did reveal some, if not drastic, improvement in the speed of the downloading and displaying those files. Finally, all users will welcome the fact that SP1 has mostly eliminated the wait for the Password box to appear after pressing Ctrl-Alt-Delete to log in.

A few other details round out the SP1 release. First, compatibility with existing programs is far stronger. On the first release of the OS, only about 250 programs sported the Vista compatibility logos; that number now exceeds 2,500. In addition, over 15,000 components and drivers have official compatibility. In practice, this means that installing programs and connecting new devices is likely to result in instant compatibility. Mind you, you don't actually need SP1 to get all of these, since Windows Update offers them anyway, but they're built into the standalone version of SP1.

With SP1, Vista now supports Direct3D 10.1, a worthwhile addition for hard-core gamers. The update also works with the x64 Extensible Firmware Interface (EFI), allowing x64 machines to perform network boots from an EFI device; Vista originally supported only standard BIOS boots and EFIs for IA-64 machines. In addition, SP1 adds support for exFAT, the Extended File Allocation Table drive partition system, which numerous Flash devices use, although these devices cannot be used to increase system RAM through ReadyBoost. Also with SP1, Vista now adds icons that distinguish HD-DVD (RIP) and Blu-ray drives from each other and from standard DVD drives, and improves connectivity with Windows Media Center Extenders.