Re: I still don't get it
Having a Velociraptor, a Win 7 machine with plenty of RAM and a spare, fast 8Gb memory stick, I have already tried this.
The answer is it makes absolutely bugger all difference, bar adding another flashing light to the box.
I reckon you probably need a USB3 stick and port to see any advantage that isn't chewed up by the overhead of running ReadyBoost in the first place when the spinning HDD is already fast.
Now, there were rumours when Win 7 was in gestation that it would provide the ability to tie an HDD and a small SSD together, to provide something like a DIY Momentus XT without the size limitations. Shame it never turned up. That'd be interesting, if only to see the interminable flame wars over the best SSD to HDD ratio this would undoubtably cause......