The discussion of ATI or nVidia could go on for ages. (Search the forum and I am sure you will find plenty of opinions)
I use an ATI 9800 AIW. I prefer the ATI cards over nVidia. The 9600 pro card is a good card at a good price right now. You could wait for the next round, but in 6 months, there will be another round and so on forever.
I say go for the ATI card now, unless you want to wait for the 9600 XT to drop even more.
You could say I've been around.