Well, the voices in anime dubs sound very... unnatural, that's my only pet peeve with them, that most of them sound off somehow, especially with female voices. It feels like the VAs try to capture the high-pitched, squeaky voice that most anime girls have, and they fail. Hard. I hardly ever find the VAs doing a good job at getting the voice pitch right.
Now, I didn't mind the SAO dub, it was pretty decent IMO. (I saw a later part in of the anime in subs, so I do know who the two sound like). In fact I've seen that recent dubs have gotten better. For one, Funimation's Fairy Tail dub is one of the better dubs out there, IMO.