There is a video on YouTube, just google "iPad3 vs iPad2" and one of the first ones is a guy who runs benchmark tests on both simultainiously. I realize you didn't ask for comparison stuff, BUT you could use the benchmark testing sites & apps he did to test your device against what Apple says, if you so choose.
However, skepticoptomus Rex we can be about everything companies "tell us" and we can take it at face value or decide to investigate further. Do cars get the stated MPG? Are calorie counts on our Doritos accurate? Will my running shoes really last me the stated mileage? Will my 4 seasons tent really work in the darkest night in the dead of winter?
There are "curves of average" to everything. If you get a magical 11th hour of battery life on your iPad, will you come back here and sing the praises of Apple? But if you get 9, hoot and holler about how they deceived you intentionally? Should you? Ah, the standard bell curve of averages...how we dislike the lower end of the bell curve! How some people don't understand the concept of averages.
Test away. It will either make you happy or mad, depends on your expectations.
You forgot if the BFG 9000 can wipe out a hundred zombies all at once as it says so on the box