I have windows 64 bit installed on my computer. Runs awesome and there are fewer bugs than my 32 bit windows xp. Just check to make sure you can get 64 bit drivers for all of your hardware. After that you're set. I have 64 bit creative drivers, 64 bit ati drivers, etc. I think it's a sweet operating system and like I said I have seen fewer bugs than I do on 32 bit. I personally recommend you get it and enjoy the 64 bit stuff coming out. 64 bit IE is pretty cool too.
You can get an OEM for around $150 I think on newegg.