I have the ThinkTank Airport Addicted V 2.0. Warmly recommended! It is well padded, and has a waist-strap (a must for any serious back-pack). It is not as comfortable as a purpose made hiker back-pack, but I found it to be the best camera back-pack, and I am very pleased. I have not tried it in heavy rain over time, but believe it will do fine. It does not have wheels - wheels take up valuable space.
I travel by air often, and sometimes I use the bag partly for camera stuff, partly for other carry-on items. It is about the largest you are allowed to take on-board large aircraft. On some smaller aircraft (smaller than a Boeing 737) it may be too big. The ThinkTank visually looks like a "soft" bag, which makes it less likely to be required to check in than a hard-shell case of the same size. I am talking by experience - my hard-shell case was often subject to careful inspection for size and weight, even if size was within limits for carry-on bags.
Finally, my ThinkTank has a small lap-top case that fits in it's top pocket. This is easy to remove for airport screening, and has saved me a couple of times from having to check in the ThinkTank. Most airlines allow a "personal item" like a laptop in addition to your carry-on. Removing the laptop case makes the ThinkTank slimmer and more easily passable as carry-on. When through the gate, just flip the laptop case back into it's pocket on the ThinkTank.