Thought I might as well stick up a few thoughts about Vista as I've been using it a bit on my laptop while slowly configuring my linux setup and waiting updated version to come out:
The Good -
Vista's Built in search - By default it's selected when you press the win key or click on the start menu, so type in the first few letters of the app or something from the document you want to open, and it brings it up in a second then it's just a matter of hitting enter to start it, or the down key then enter if theres a couple of apps with similar names. For starting apps I'd say it's pretty close to gnomes deskbar tool though it lacks the useful plugins deskbar has for web, calculator etc.
Also as a search engine it seems pretty decent, though maybe not quite up with Googledesktop in some areas such as text preview.
System speed - It's pretty good, vista finally utilizes all available ram to cache apps and other stuff of interest in a manner similar to linux, as a result the system is rather snappy. At least on laptop with 3GB RAM.
Sidebar - A widget system that seems to work fine a little slow starting, and some what RAM hungry (70MB for 6 applets one of which has my address book loaded) but CPU lite. Also could do with a few more applets and a hot key to bring them to the front ie F9.
Security - Requesting permission to make system changes is good, still not with out it's share of problems check out the BAD.
File System Layout - The new file system layout with /users makes more sense than the old /Documents n Settings. Also placing the various media, catagory and search folders at /users/username/ makes more sense than the old /Docs/username/My Documents/.
Windows network center - Nice clear layout of how and what your connected to.
3D desktop - Somewhat RAM hungry (100MB 9 apps open + sidebar) but again fairly CPU lite when used with a dedicated 3D card (10% single core when moving a video window round while it's playing). The 3d switch app mode is alright but nothing great, much prefer the linux cube, wall, or OSX expose.
Appearance - Not bad not brilliant either, far, far better than XP's though if your computer can handle Aero. The new icons are nice and the file previews and folders showing previews of there video or image content is nice.
Windows Defender - Spyware/malware protection, useful but hard to know how effective it is.
Windows Mobility center - Quick access to laptop specific settings.
Security - Permissions can get out of hand to create a folder and rename it in a section of the drive you don't have full permissions too requires 4 confirmations!
1) Warning you will need permission to create the folder
3) Warning you will need permission to change the foldername
That's 4x you need to click continue in an admin account! UAC really needs a cooldown period or something similar like linux, ie once you give your self permission you have admin permissions for that Window and it's contents until you close the Window.
It also needs some method of saying hey I trust this app this can be run as admin as long as it doesn't change with out me being asked to confirm it each time!
Compatibility - Some games are quite mucky to get set up and some of the vista security options can result in odd things happening to them. Compatibility mode + Admin permissions has worked so far for me though.
Performance - For gaming at least seems somewhat slower than expected, this may be due to still fairly early drivers for vista and current generation hardware.
Settings - The settings have been rearrange somewhat, not sure why but compared to windows XP sometimes things aren't where you expect to find them.
Size - An operating system with out any applications appart from basic email, internet and IM shouldn't take 8+ GB HDD space!
Overall I think vista is a nice upgrade from XP if your computer is fast enough to handle it properly and if you don't have too many legacy programs.
Windows Vista, with a few changes.
My previous linux desktop.