I used Vista Home Premium that came with my dell in September of 2007, I hated it. DX10 was HORRIBLE for games, Vista ate 52% of my RAM. Call it pre-caching or whatever you want, it still SUCKS when it caches an entire freaking GAME into the RAM when I may only play that game once a day, leaving me with like, 80% RAM usage. Average idle for vista with everything turned off was about 5% CPU usage on both cores, 52% RAM usage, higher than normal temperatures (CPU idled at 110 Idle's at about 90F now with XP), and if I listed everything I couldn't run on it versus what I could run on it. You'd have a really long list of incompatibilities, and a REALLY short list of compatibilities.
Long story short, Vista is in my opinion, a virus. It eats system resources like it has a bottomless stomach, it slows the system beyond belief, and most of all, it causes more instability of the system than any Trojan I've ever seen alone. I couldn't even run Counter Strike Source on low settings worth a crap on my laptop with Vista and DX10. I can run it on high @ 1440x900 with XP and DX9, same goes with MANY other games. Oh, and in vista, I noticed that near any reflect maps never loaded properly in any source based game. Dunno if it was the source engine, the drivers, or DX10, it don't happen in Windows XP SP2.
Point being, Vista isn't a step backwards, its a f***** full blown LEAP backwards to Windows ME. Oh, and not only does it BLUESCREEN like nothing I've ever seen, it also has red, and even green screens! The h**l is up with that? I mean honestly, I only need one SOD, I don't need three, or even two, just ONE! That's just one thing that annoys me about it, its caching is another, the UAC security is another, need I go on? I can't so much as overwrite a file without it blaring in my face like its a breech in pentagon security! I don't need that crap in an OS, I need something that while stably run my games, and other apps, and not eat my system resources like a thousand Trojans.
So yes, when you install vista, unless you want to re-learn a bunch of new "Vista Compatible" Applications, it is like the Mojave desert, BARREN, AND EMPTY! Making a move is life threatening even! The stress could kill you in a matter of years, I'm sure of that.