I've not had the time to get it up in the mountains yet - hopefully at some point in the next couple of weeks I will... I drove from Denver to Cheyenne, which is a fairly gentle increase of 1,000 feet over long shallow grades over about 100 miles... about 37 MPG going up, over 40 coming back. That's at speeds between 75 and 80.

Power is tricky - the accelerator pedal isn't linked for hard acceleration (my 05 Accord V-6 would leap off the line), but if you need the power, you'll get it - just step on it. Driving with a CVT is interesting, as posted elsewhere here - the power delivery is so smooth that at higher speeds you may not be aware you're accelerating (also, the car is so quiet, except for the times when you're really using the ICE - like on steep hills)

I've read in some posts that I shouldn't expect the same gas mileage or power at high altitude (in both directions) - I don't know if that's true or not, and I have nothing to compare it to, but I'm happy with the mileage and power so far.