Oh, he is a biter for sure. But he's a love-biter. I've never seen him actually angry with the exception of when the vet put a thermometer up his ass, and then he didn't attack, just hissed and cowered.
He has intense play-aggression, though, which I am trying to train him out of. I don't think he was properly socialized as a kitten, and I suspect part of the reason he was surrendered was his biting. It's so clear that it's affection, though, because he never leaves a mark and doesn't use his claws. He shows no signs of anxiety or true aggression when he does it (no dilated pupils, puffy tail, hissing, or flat ears), and he often licks and grooms when biting. Still, I want to discourage the behavior.
I'm not using any negative reinforcement, just structured playtime so that he's not bored or lonely, and completely ignoring his bad behavior so that he learns he won't get any attention at all from it. He seems fairly smart for a kitty, so I think I can train him up. He's already learned his name, "up", "down", and his meowing for attention has gone from hour long sessions to about five minutes before he gives up. I'm assuming that his previous owners just didn't have much cat experience or patience (or maybe they had small kids, he wouldn't do well with kids).