From what I can gather about ReadyBoost is that using the USB key isn't a replacement at all for system ram. What ReadyBoost does do is act as additional virtual memory space - instead of using your relatively slow hard drive for virtual memory storage, it uses much faster flash memory to cache and help offload the Virtual memory to the USB key.
Apparently (from what I have read anyways) is that if you already have like 2 gigs of ram (or more), you really won't notice all that much of an improvement even with ReadyBoost enabled. Even if you have only 1 gigabyte of RAM, you may not notice that MUCH of an improvement. I think Microsoft has the right idea with ReadyBoost, and I hope they expand support for it, and tweak it to allow for better performance gains. With the advent of reallllllly cheap flash drives, more people would be apt to take advantage of Vista (and therefore buy it) if they knew they could squeeze extra performance out of it in a fairly cheap way.
Who knows? Maybe if flash prices keep dropping, (and if Microsoft can truly make ReadyBoost access more like RAM access with better performance and support), mainstream ram prices will hopefully follow suit to compete.. That would be a sweet proposition, now wouldn't it?
