If you can actually hit 50+ mpg on the new prius eco at a real freeway speed (75-85) i would be seriously impressed. However i would still rather get a Volt if i was in the market for a ultra miler.
I would say a typical "long" commute is 50 miles one way. If you can do half of that on electric and then 40 mpg on gas on the return trip you still got 100 miles for one gallon and a few KWs. Some people can charge up at work and use even less gas.
I do give credit to the Prius for having incredible durability across the generations. Who would have though with that much technology that it actually holds up? A battery swap isn't the end the world, and one of the only chronic issues.