Been reading the threads about it on 2+2. Got depressed that two of the first questions were 'What's the rakeback?' and 'Can you use HEM?' Regs gonna reg I guess.
It's a start for American online poker, from what I can gather so far Americans who are in Nevada (don't have to be residents, just in the state borders) can play on it. I haven't yet found any information if non-Americans visiting Nevada can play on it yet. They had some software funk the first day but a lot of people are somewhat excited.
I read somewhere that tourists can play on it and even sign up from abroad in anticipation for their Nevada visit. So yes this is open to foreigners, you just need to be in Nevada as you play.