After reading about oil ad nausium both in oil threads at many forums and doing google research, i've come to the conclusion any good oil is going to be as good as the next if you change it VERY often. The shear factor in bikes with shared oil between case and gear box is what kills oil much quicker than in a car. It's said 3k is the point at which it loses a large portion of it's lubrication properties. So may say change it every 3k instead of worrying about oil types. Thats from what i've read seems to be the overwhelming general consensus.
That said, i think no one would disagree that you can't go wrong with M1 bike oil or amsoil. But as far as which bike oil has been the #1 most touted overall in my searches i'd have to say it's probably motul. I've never heard a bad thing said about it, only real positive things. It was also recommended to me by triumph a mechanic i probably respect more than any other triumph mechanic. So that would be my choice.