I'm runnin' redline 10w40. works great!
I have run mobil 1 10w40, honda hp4 10w40, spectro 10w40, golden spectro 10w40 and they all work good. I would stick to 10w40 unless your bike runs hot or your driving around in the summer in stop and go traffic.
I've always used Golden Spectro Semi-Synth with great results. Of course, if you change every 1500mi like I do, nearly any oil should work just fine. In my past experiences, full Synth's have given way to clutch slippage.
Synth oils are probably the best thing you can feed one of these oil-cooled engines... they're very stable over a wide range of temps and typically don't lose properties as quickly as the dino-base oils do.
The only "downside" to them is that they lubricate so well that some wet-clutch bikes can't handle them well- my Bandit1200, for instance... I'd definitely be running a synth oil (and probably will once I upgrade to a lockup clutch) but the clutch pack doesn't have enough torque capacity to hold the engine when synth is in the sump.
So yeah, there are cases where synth oils aren't a good choice- but it's more due to shortcomings of the bike than of the oil.