PCstats takes a look at Vista’s ReadyBoost feature. Decent article. Worth a read.
…Even with 512MB of system memory, ReadyBoost only increases performance in the benchmarks by a few percentage points…What the tests don’t show, is that applications within Windows were clearly quicker in loading…For memory configurations 1GB or higher, ReadyBoost does not improve system performance, at least not enough for you to notice it…
Microsoft Windows Vista & ReadyBoost: Does it Make a Difference?