I dunno... I'd probably have to try to come out of left field in pseudo-typical HoserHellspawn fashion and say something like "Hey, Mike, if they ever wanted to put you on the cover of GQ do you think you would shave off the moustache?".
Back to the thread... as the main creative brain behind Opeth, I think you just sort of immediately get the mindset that Mikael would be the most interesting to talk with for awhile. Although, again, based on what people are saying Peter seems like a cool guy, and perhaps he might be the most interesting to meet. No matter who it is, though, I'd probably try to discuss something other than music as they must do that all the time. Either that, or the Wayne and Garth approach...
Although, come to think of it, another possibility is that I could end up spending my time trying to keep Opet from throwing herself at Peter and embarassing herself. (Of course, this would require us to be in the same place at the same time as well as Opeth, which given to the fact she's in R.I. and I'm in B.C. would be unlikely, but it's still a funny comment to make nonetheless. Right!) Then again, Peter might very well want that, so... hmm...