i think it is time for me to speak up as a student with a 17" powerbook. Now to be honest, there are times when I wish I had a tiny little 12", but i think more often than not, I am amazed by the 17" and its abilities. to be fair, I had a desktop as a freshman, and decided to go laptop this year because I thought it would make travel to and from university and home much easier, and it does. but it being my first portable since an old 286 that weighed over 15 lbs, I think it is tiny. I will agree the 15" seems like a great compromise, and you've got to make special accommodation for a bag that can hold a 17" and not look suspicious or ridiculous. I found one that is nice at a local store, and I don't mind carrying the system around all day, at least in terms of size and weight annoyances. What I do mind is the super protective feeling I have when it is with me. I would take down a bear to protect the thing from scratches or dust, and I walk a bit more tenderly with it on my shoulder.
as for in lecture, it depends on the hall/classroom. if you have desks or tables, it is no trouble. ditto for lecture theaters with those little desks that fold to the side. the only trouble is with rooms that have chairs with fixed side desks, that don't move (and a lot of them are slanted) there is no way to use my powerbook with those things, but I would guess you can't use any of the other sizes either.
on the whole, I wonder sometimes if I should have gotten a G5 and an old ibook, but 90% of the time I could not be happier. good luck with your decision!
as for in lecture, it depends on the hall/classroom. if you have desks or tables, it is no trouble. ditto for lecture theaters with those little desks that fold to the side. the only trouble is with rooms that have chairs with fixed side desks, that don't move (and a lot of them are slanted) there is no way to use my powerbook with those things, but I would guess you can't use any of the other sizes either.
on the whole, I wonder sometimes if I should have gotten a G5 and an old ibook, but 90% of the time I could not be happier. good luck with your decision!