I've got a relativly small Kelty day-pack that fits my 4x5 and extra lens, several film holders, filters, cable, cloth, etc. It's a normal pack for backpacking, but I really like it (of course, I do a lot of day hiking when I shoot tho...). I always take it with me as a carry-on when I fly (several times a year, fits nicely under the seat, never really tried putting it in the overhead bins for fear of it getting squashed by everyone bringing their roller bags on that I can't imagine fit the maximum size allowed), and have never had a problem with it. To me, it's super light, and even has a waist belt strap thingy on it for heavier loads. No wheels, but I'm usually shooting in places that I think wheels wouldn't survive the trip or help you out very much. Also, in some places like certain wilderness areas you can't bring wheeled things in, including carts/bags with wheels.

Good luck.