I'm now running a full release copy of Windows Vista and I have to admit it doesn't suck like I initially thought it would. I ran a number of the betas over the course of the past year, and fully anticipated the final product to be big, bulky, and extremely slow. I'm on an 'older' laptop (1.6GHz 1024MB RAM) with a crappy video card (Mobility Radeon 8000) and a Vista System Rating of 1.0 (which appears to be very low) and it runs perfectly smooth, even with Aero Glass as my default theme.

Pros:
- I read this before I installed, so I've noticed the new sounds, they're not annoying which is good.
- I like that Alt-Tab now includes a "Desktop" feature, so you can now switch to a blank desktop in addition to any other running application
- Better security, you are prompted for your password (much like OSX I think) before you can install a program or make a change to your system
- Aero is pretty, I like that it's black

Cons:
- It's Windows XP with a new theme, I haven't seen any reason to recommend that anyone upgrade yet
- Better security, you have to enter your password for every little thing (even to let windows update to run). I don't mind this because I can see why it is necessary, most people don't have passwords on their XP install and this may confuse and annoy them.
- The password prompt's aren't always very descriptive. The first time I visited a website required flash I was prompted for my password before the site would load, and the dialog box only mentioned it was trying to install "an add-on". There was no mention of the fact that it was Adobe Flash, or that it was digitally signed.

Other Observations:
- "Run" isn't on the Start Menu anymore, but if you press the Windows key you can simply type the name of the program (or the web address) and it will start.
- Windows Gadgets try to mimic OSX's Widgets, but so far I hate them. They take up valuable desktop space and there isn't an auto hide option. I use a Google Start page for my RSS feeds so I don't find Gadgets all that useful yet. I think in OSX they're hidden until you press F12? (Yes they'd probably be good on a widescreen display, but I hate widescreen laptops).

Conclusion:
I would recommend Vista if you are buying a new system, or if you can get it for free. I'm on a work laptop, so it cost me nothing to upgrade, but I will continue running Windows XP at home for the foreseeable future.

Update: I initially thought they had removed 'telnet' from Windows Vista. Which would have sucked as it's a great troubleshooting tool. It turns out it's been turned into an optional feature which can be installed following these instructions.