I have nearly all OS under the sun in my computers at home - 95, 98, XP, Vista, Ubuntu, Fedora (yeah, both are Linux, I KNOW)... Only no macs (that is Unix in disguise
)
New computer? Vista.
Despite what the naysayers say, its much better than XP, and the market for apps and drives has matured enough so you can use it with no (or little) hiccups.
If you'r an advanced user, disable User Account Control. If you dont know HOW to disable it, DONT disable it - you dont know enough yet. It WILL be annoying as hell, but it WILL protect you. I caught a virus hidden in a no-cd patch for a game via UAC - the patch was trying to wite to /windir/system32 - something a patch shouldnt do. It is way safer (sometimes annoyingly safer), and has a much better interface - not only looks-wise (way past the time for a OS to use the uber GFX cards everyone now has), but usability-wise too.
For example, in XP, you open an explorer window in say... the LFS/Data/Setups folder. In those 2 billion files, you want the one named "XFG_somethingorother". You hit "X" and it will select the first file with the X letter. And thats it. hit "F" and it will go on to the files starting with the letter F.
In Vista, however, you hit X, and it pops to the "X" files. Hit F and it will go to the "XF" files. Hit G -> "XFG" hit the underscore "_" and "XFG_" and so forth.
Makes it finding file a HELL of a lot faster. Its an idea imported from linux, and a very good one. (though linux will show you a little box so you see what you've been typing).
In the start menu, you got a small box that is the equivalent to the run command. HOWEVER, this box can also be used to SEARCH the start menu.
Pu in the box "paint", DONT hit enter, and it will find the paint shortcut in the start menu for you. (or just type PAI and it will show you all the shortcuts with PAI).
Invaluable when, like all other users, your start menu is a mess of 2348796429874263 differente folders and 2314981239048761 different programs. Even better, the typing cursor is automatically put in the box when you click the start menu, so to being a prog you dont really know where it is, just hit the start menu (or windows key, a-la XP) and type the first few letters of the program. No need ot use the mouse at all.
Theres several of these small additions (like the omni-present search box on all windows) that REALLY help your life.
Going back to XP, though its more "familiar" feels somewhat clunky and clmusy. Navigating through endless folders just feels weird (in vista you got those dropdown foldertrees from the "triangles" in the address bar of the explorer window).
On an old computer - not worth the cash.
On a new one, though - go for it.
HOWEVER - THIS IS IMPORTANT.
If your computer is dual-core (as it should be) get Vista 64bit.
64-bit vista has about 70% less problems than vista 32-bit. 32-bit vista IS XP on a drag. (which is just win98 in a drag, BTW).
Also, get 2 gigs ram at least.With vista, firefox, and some otehr apps, I got 30% free physical mem free (from 2gigs). 1 gig is NOT enough.
EDIT: forgot to mention I also tried vista 32 on this computer, and it was hell - diVX didnt work, S.T.A.L.K.E.R. kept crashing, had a zillion little problems that had me go back to XP (this was a year ago). I got vista 64, and no problems so far.
Gotta love being a computer science student with free access to loads of microsoft products!