Man, thanks for all the thoughts so far, really making me think about what I want. I guess I am reluctant to go with less than 6x7 because in the final analysis I really just want to get away from the small negative and focus on getting the best quality. On the other hand, I'm not sure I'm ready for 4x5 - mostly because of the $ to shoot, I would have to find a 4x5 enlarger, etc - I just don't know how much I could actually shoot it at this point.

Regarding the 6x4.5 and 6x6 camera setups - Let's say the body, and 3 lenses - a wide angle, standard and medium telephoto lens - are they really that much smaller and lighter than a 6x7 setup? I mean are we talking a pound and a few fractions of an inch difference, or are we talking like 3 lbs lighter and several inches smaller all the way around?
When I shot 35mm it was usually with a Maxxum 7 or 9 body w/ vertical grip, and wide to medium zoom plus a tele zoom - so that's about the size/weight I was used to carrying. I don't think I would mind a little more bulk and weight for so much better quality at this point, but...then again, maybe I would on a hike?