On lateral stability I think aircraft like the F117 are basicly unstable and still fly.
A lot of military aircraft start with an unstable design and use control electronics to stabilise them for flight. This gives a very fast response to control input, useful if someone's shooting at you or you need to shoot at them. Commercial aircraft tend to be designed for stability so they don't rely on a lot of control software to just keep them in the air. You don't want to be doing barrel-rolls in a passenger plane (707 excepted...) just because your hand twitched.