I've had these bibs for about 4 years now and couldn't be happier. Construction is solid, and I only have a few small tears from crampons and skiing into tree branches accidentially. I'm a big fan of the articulating knees and kneepads. No problem lifting my legs when I'm climbing, and the kneepads add some protection when ice climbing and keep the knees warm when kneeling on snow. The full length side zips are a must for me, great for ventalation, but mostly allows for a speedy approach in just base layers and a quick layering process without removing boots. I'm 5'10" 190 lbs and athletic and the L reg fits just fine.
As a product tester for Gore, I'm keen on the Gore-tex line of products and am a big fan of their pro shell material. I typically wear a single base layer under the bibs and have no issues with breathability or temperature regulation. As always, they keep me dry, even when snowmobiling. I alway end up repeatedly getting snow on the seat, and melting it with my bum. With other pants this results in a cold and wet bottomside, but problem solved here.
What would I change? The full zipper between the legs is a good thought, but really cumbersome to manage going #2 while wearing. I've done it plenty of times, but your other layerscan only be pulled down to the crotch of the bibs regardless of the zipper being open or not. Other than that, those sneaky little chest pockets must be zipped at all times if you don't want to lose the contents. I've managed to lose a camera in one instance, and ID, credit card, and 40 swiss francs in another.
I will definitely get another pair if mine ever die.