I'm running the windows 7 64 bit OS and I can say it is very smooth with all the games I have on, these include SH3 and SH4 with loading speed improvments and frame rates on both. With rumors that Windows 7 could be released as early as October I think you would be better waiting and just move straight to Win7 if thats the way your inclined to go.
my 2 cents
Steve
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