Well I don't know what kinds of programs and resources people are using but you typically will not see a change in performance with multiple gigs of ram and ReadyBoost.
I recently purchased this new toshiba laptop with 8gigs of DDR3 1066MHz, accompanied with the intel core i7 620m processor and I have not only used ReadyBoost for my system but noticed a significant difference in the loading and processing times.
What do I do you ask? Design buildings using AutoCAD/AutoDESK/Architectural Desktop Suite pack 15.6. Fully installed with all of its tools and packs takes up a whopping 42+GB of HDD space, and each file I've compiled so far is no smaller than 2gb(the bigger projects take up 20 times that if saved properly)
I'm currently running 2-16gb(32gb compressed) instances of ReadyBoost at any given time on my windows 7 ultimate system and I definitely need it. Originally when I was looking for a new laptop to replace my Toshiba Satellite L505 series, Intel i3 w/ 4gb of ram, I was looking for a quad core, local stores didn't carry one and the infamous "geek squad" insisted that I did not need a quad core for anything, then again they've never used architectural desktop.
Anyway, to say the least the ReadyBoost definitely helps out if you're begging for more system resources and NEED it. And by need it I mean really, truly need it. If you're surfing the net, emailing, gaming, whatever it is you may be doing, you probably won't notice a considerable difference, even if you're really looking for the difference. While some may claim 5 - 10% increase in response time, that's great, more won't notice it unless they're really killing their system for resources. I'm just glad windows 7 unlocked it from their vista version, to allow more capacity because I can definitely use it.
So far, I've noticed that the best way to get the speed and have it working all the time is by using SD cards in an empty SD slot(for a laptop anyway) Thumb drives stick out and use up usb ports. Not to mention you can set an SD card up to run while windows starts up to free up load time and reduce program load times by up to 50%. Not only that, but when I used a typical thumb-drive, I actually got the BSOD while running a few system scans(BSOD went away when I removed the thumb-drive), so it's not the best form. If you have SD and the slots, I suggest using those first. Kingston 16 G SDHC is the way to go for ReadyBoost...
Sorry for such a long post