It'd be great if the requirments for 7 end up being around Vista's. By then it'll be a lot easier to run. Even though we're about 2-3 years off from getting it. By then DDR3 is going to be the standard, and hopefully we'll see 4GB of whatever DDR standard is for DDR3 by then (DDR3-1600?), for under $250 or so. That may be dreaming, but it'd be great.
Vista 64-bit runs like a dream on 4GB.