If I use a carry-on rolling bag, I use an Andiamo Valero 1 suiter, which is a tank. But most of my carry on travel is done with a shoulder bag. My favourite is a black Hartmann Tri-Zip with 3 compartments that butterfly open flat (and have tie downs), a large pouch on the outside surface and a sleeve pouch and smaller zipup compartment on the inside surface. To replace the crappy Hartmann shoulder strap, I use a great one from Red Ox, that is very comfortable and clings tenaciously to my shoulder. It is amazing how much stuff I can get into this bag, and if I don't have to pack a suit, I can travel for a week with it. I also have a similar, but 2 compartment with a third smaller compartment bag from B&R. Both bags are discontinued, but can be picked up on eBay for a song. For those of you who haven't tried travelling with just one shoulder bag, check out
http://www.onebag.com - it could change your life!