No wobbles at all if you keep the speed down. I don`t think I`ve gotten any up to about 25 mph or so- trying to be extra smooth, I had it breifly over 40 without wobbles, then decided I was pushing my luck.
The "one bag" thing is a minor hassle for me. I can live with it, but prefer to separate stuff more. FWIW, I bought mine with the BOB dry sack and don`t use it (that bag) any more. It`s very rugged and undoubtedly rainproof, but it weighs about two pounds by itself. I found a much lighter, but not waterproof nylon dufflebag at the thrift shop that I like better.
$400? I`d check around- I think they still go for about $300.