I'm pretty sure the MBP will be fine at airports, won't work when flying economy and will be OK on a train providing it isn't too crowded, but I'll try all of the above in May and report the findings for anyone interested.
As a side note, I'm really loving the MBP. Just pulled it out as part of a presentation this morning. It was just a “sit round a conference table with a few people” kind of presentation, displaying some comp's they'd provided us for turning into HTML/CSS and it was impromptu, but having the 17” screen definitely made the experience better for both our resellers and us.
Definitely loving the 17” so far . . .