I carried the iPad 2 just in a sling pack from Eddie Bauer. Not a lot of protection - and I noticed I wasn't all that gentle when putting down the sling.
This is the next generation - but you get the idea - no real padding
Sling Pack | Eddie Bauer

I got a Built sleeve and backing from REI-Outlet for something like half off ~$25 so I bought it just to try it out. I put the iPad in the sleeve most of the time.
Travel Pack for iPad 2 | BUILT

That Built hard back - fit over my leather Zagg - onto the New iPad - a little bit off for buttons - but I think the camera was OK. Anyway - I don't use the plastic back much - I used to put it on every now and then.

I flew a lot with that setup and haven't had any problems. The only issue I have is with the smart cover. My blue smart cover started tearing around the metal bar so it slides up and down now - making it worse. It may be because I used to keep the iPad in my backpack - next to my MBP. I am keeping the New iPad in the sleeve - hopefully it saves the smart cover.