I thought it was pretty good. Not nearly as cleverly thought out and written as most of the Pixar movies are (and, yes, I know it isn't a Pixar movie), but it certainly did not suck on the level that many of you are claiming.
It had some nice tips-o-the-hat to real aviation, but my biggest disappointment is that, unlike the obvious references to real-life NASCAR/F1 cars and drivers in Cars, there were no such references to actual Reno or Red Bull racers.
Yes, there was a Gee Bee, and a couple warbirds (a Corsair, a razorback Mustang, A Sea Fury, and something else that is slipping my mind right now), and Ripslinger is very close to the Nemesis NXT Sport Class racer, and there was a passing dialogue reference to the post-WWII Cleveland Air Races...but that was it. There was a Reno Air Races poster on Skipper's wall, too.