My main PC before this (Conan-01) has a single 7870. The biggest hurdle, though fairly easy to adapt to, was getting used to the Nvidia control panel. Aside from that, I did find that turning SLI mode on or off sometimes resulted in black screens when using the latest beta drivers. I don't think I'm having trouble using the current non-beta drivers though.
The case is nice. The only issues I've had with it so far were some of the screws being ridiculously hard to unscrew the first time and I can't seem to get the LED on the back to work, though that's probably me doing something wrong.