I'm having an occasional problem with Win7 RC and hybrid sleep. It seems that if I arrive back at the computer just as it's going into sleep mode and I hit a keyboard key to wake it up (I usually use the Shift key as it's harmless), the system goes into a black hole and there's no way to get it started again short of doing a power cycle.
The good news is that since it's in hybrid sleep mode, it comes back up properly and continues exactly where it left off, even though the power was cycled. The bad news is that the resume takes a LOT longer than if the data was still sitting in RAM, which kind of defeats the purpose of "sleep" mode.
I'm hoping that this problem was fixed in the RTM version. Of course there's also a chance that it's a BIOS issue with my Asus P6T6 WS Revolution motherboard.