I was pretty pleased with Windows 7 beta running on my netbook (LG X110). The beta ran speedily, especially with the 4GB Class 6 SD card that was used for ReadyBoost. The only problems I experienced were that it tended to forget settings; if I muted the sound, the sound was back on after a reboot.
Before leaving on a three-week trip to Europe, I updated to 7RC, because I knew that the beta trial period was coming to an end. I figured it would be as good as the beta, but with fewer annoyances.
Big mistake! The "release candidate" ran dog slow. Applications would take 5-10 minutes to launch. In the final hours before I needed to leave for the airport, I quickly installed Presto Linux as a dual-boot program and as a speedy alternative.
During my trip, I tried to figure out why 7RC was so slow. After about two weeks, I determined the flaw in 7RC: ReadyBoost. When I removed the SD memory card, 7RC ran at a normal speed -- albeit somewhat slower than 7beta with ReadyBoost.