Personally, I am happy with my Vista. It is not substantially better than XP but it's no worse. I am running Half-Life 2 without any problems on my HD 2600 XT.
If you buy Vista Ultimate, you get both 32-bit and 64-bit. I don't think Vista is going to die yet. XP didn't really take off up until SP1 was released. Also, I doubt that Windows 7 will be released anytime soon. MS is rewriting the whole Kernel so that got to take a long time.
As mentioned above, 32-bit (in XP or Vista) is the way to go. However, you will be limited to 3.12GB of memory. 64-bit drivers aren't ready yet so it is a big problem. It might take a year or so to get its act together.
No foreign sky protected me,
No stranger's wing shielded my face.
I stand as witness to the common lot,
survivor of that time, that place.
- From 'Requiem' by Anna Akhmatova
