You will find Garmin haters for virtually every product they make. With Garmin you are sort of a Beta tester in the beginning. It usually takes them a couple of firmware and software fixes before they settle down. Personally, I really enjoy my 520 and I'm still finding features on it that I didn't know where there. Has it ever froze up on me, yes. Have I ever lost ride data, yes. But I still take it with me on every ride.
If you want a detailed rundown check out DCRainmaker's site. His reviews are quite possibly the best on the internet.