Whelp thanks to my job i've had a WIndows OS Developers VLK for the past year. Pretty much 10 Licenses to all the Windows OS's and Office. I have an addiction i like building myself new comps. So I have plenty of boxes to test shit out on. So lemme throw my 2 cents into this fine thread.
Now in the box connected to my TV. A Pentium 4 2.8GHz with 1GB of RAM. Originally it had Windows MCE (Media Center Edition) 2005. I use that box to watch and record TV with a PVR card. Lets call it a windows DVR. Got a couple 500G HDs in there to store all my recordings for roommates and myself. This was the first box i upgraded to Vista Ultimate. As with all new OS's finding new drivers wasn't easy. However, it did except alot of the XP drivers which held me over till manufacturers came out with Vista drivers. For a box that is used to limited web browsing, email, and Media Center. It runs smoothly and changes were minimal.
My older gamer laptop a Dell P4 3.2GHZ with 1GB Ram with a Raedon 9800. I updated this one next. It was hardly used and basically its my bitch testing machine. My game of choice lately has been WoW so much of this coming paragraphs will be using WoW as the game variable. Now in XP it the lovely video hell known as Shattrah i was getting 20-25 fps. This is pretty decent considering i like to keep my graphics setting high and the amount of video intensity in Shattrah. After the conversion to Vista this machine took a hit. From that 20-25 fps to a slide show of 7-12 fps. Now i kinda chalked that up to this being an older machine. So lets move on to my newer gaming laptop.
This laptop is a 2.2Ghz Duo Core with 2GB RAM and a GeForce 7600. Now once again as WoW as the variable. This one i was kinda surprised at. In Shattrah i was getting a solid 30-35 fps and its was great. However over time is started to drop. Within about 2 hours it was down to that 10-15 fps range. Solved by a game restart to get is back to normal, it was just odd that it needed a break. This laptop is brand new and came with Vista Ultimate x64 installed.
I still haven't tried Vista on my main gaming rig. Altho my main gaming rig hasn't been upgraded in a while and is the same one I rocked last HF Lan almost a year and a half ago.
I have test server at work i play around with. It originally had Server 2003 but i recently changed it over to the Server 2008 Beta. Setting up the various servers and services is a huge pain. It was much easier in 2003. IIS 7 now allows multiple sites with different addresses to be running on one machine. Altho its still very buggy with PHP and SQL databases. It has a hard time recognizing which SQL database you are running. At this point I still prefer to use my MaC OS X box with apache for websites.
Vista which in client or server form for me has its pluses and minuses. I do agree with Keith on the fact as service packs come out, it will get better. Microsoft can ill afford another ME-esque OS disaster.