My wife bought me the Porter (expedition) about 1.5 years ago for family trips. Before that, I used to use a Dana Designs terra plane (about 7 lb for pack alone).
I'm pretty happy with the expedition pack, and it has become my go-to winter pack as well. The compression system is great. I've shrunk it pretty well around 9 lb of gear and had it stuffed to the gills with probably 35-40 lbs of gear. Not sure about exact weight, as I make it a practice not to weigh family stuff, but I carried 3 sleeping bags, 3 pads, tent, extra changes of kids clothes, sweaters, jackets, real food, kids toys, etc....
It is a great platform for strapping skis and snowshoes, is built tough, has just the right amount of padding, and the waterproofing is nice. Overall a great pack that I would buy again in a heartbeat.
As far as weaknesses, a wraparound hip belt would do a much better job when carrying heavy loads. I also have slight concerns about the way a couple seams were sewn (see below), but this has not yet manifested as a problem.
When you're with Dora it's time to explore
Seam under tension. I reinforced this area with seam grip and have seen no change with use.
See the thorough rolling review on this pack by RJ for durability info.