Well my only complaint so far is a glitch I notice with headphones with built in mics. When you plug it in it disables the mic. And when your phone does go on 4G the battery life turns atrocious.
With that said this phone is very impressive. It is extremely fast. Games play way better on it than it did the incredible and the sound quality on calls are amazing. The 4G although it eats on battery power like a homeless person having a steak dinner, is incredibly fast! This is the smoothest Android phone I have ever touched, even with the usually laggy sense. I had the iPhone 4 for a couple days before I took it back to get this and the Thunderbolt is faster than that even without Dual core. So if you don't mind bad battery life and can afford an extended battery then I say go for it. Unless you're not really into large phones then don't.