This works great! The only issue I have with the program is that it doesn't minimise to the taskbar properly, and doesn't execute at startup with the "multiplyer management" enabled by defualt.
Well, according to the readme all You need to do is add "/HIDE /CQ" to the shortcut.
Regarding the 0,8V limit; it's the lowest official VID, as 1,550V (IIRC) the highest. Anything higher or lower would require BIOS setting for it, or by manually soldering a resistor somewhere into the VRM, which would make a constant decrease in voltage, say 0,1V. Then all SW voltage settings would actually result in 0,1V lower than the selected value. But as Linus mentioned, the 10W mark is (nearly) obtained at 800MHz/0,8V. One could go even lower by lowering the FSB, but that is not so beneficial.
Switching between the states requires the CPU to be halted, I guess. So by switching too rapidly will lower the performance a bit. But either AMD or Intel advertised that "their CPU will change speed up to 30 times per second accroding to usage", so 200 ms is well in "safe" region.
Also, while gaming, the game might not use 100% CPU time all the time, which could cause jerkiness as the CPU changes states. I've seen this with some games combined with CPUIdle, but the principle behind CPUIdle (HALTing the CPU all idle time) is different from CrystalCPUID's. So YMMV with CrystalCPUID.