Long highway commute.. Is Prius good for this?

I have frequent 200 miles 'commutes' (up to a couple of times a month). I've done two in my three week old 2010 model III, and it has been great. The engine is usually inaudible except going up hills. As others have said, road noise is the only real issue, depending on the road surface. My family agrees that for the first time, we can have a comfortable conversation at highway speeds. By the way, so far in this new car, 70 mph is giving me about 49 mpg (calculated from fill-ups, not the computer), with an overall average of 53mpg. I expect it to get a bit better as the ICE gets broken in.

 

I've heard the same thing (though not tested it) - it's because of the 17" wheels. With the 15" wheels, there's more rubber to cushion and absorb noise from the tires hitting the road, while the 17" rubber is stiffer and transmits more noise.