My best so far is my current bag, a Mindshift Gear Backlight 26L.
It's a good size for a 3 zoom K-1 kit (I have the D FA 15-30, 24-70, and 70-200) plus accessories and either a speedlight (V1 in my case) or my A*300/4 tele.
Seems rugged and has room for some non-photo stuff like a laptop, lunch, jacket, etc. It's not small but would work for carry-on.
For a much smaller kit I like my old Crumpler Four Million Dollar Home for a K-3 and 3 primes (15,40,77). It works for the K-1 prime kit too (24,43,77) but it's a little tight.
The worst bag was a funny little sling bag that came with my 645D in a bundle from Amazon. I did not see a brand name but it's total junk and I doubt the 645D body would even fit in there with a lens on it.