I recently rented a Toyota Prius in Jackson Hole Wyoming. I drove it through Yellowstone Park, out the west entrance, south through Idaho and back to Jackson. The hybrid really surprised me. It had enough power to really go when needed, but got great mileage when you drove normally. Through the park, speeds ranged from 55 to 35 in most places. A lot of up and down hills. The Prius handled them well. On the uphills, the engine and electric motors were working, and on the downhills, the engine is off and the batteries are charging. The only place I doubted the capabilities of the Prius, was going up Teton Pass. It was a 10%grade climb. The car sounded like it was in first gear doing about 8000 rpms(no tach). Going down the other side, we used engine braking(engine off) and the batteries recharged completely.
On this loop, we averaged 48 mpg! All in all, I think the Hybrid did very well and would consider buying one. I've been told by a Toyota dealer that it would be wise to trade it just before the battery warranty expires. It costs like $5000 to replace the batteries when they fail.
Hope this helps.