While it's not marketed as a carry-on bag, I've started using the Patagonia lightweight duffel for my trips.

It weighs 14oz, and while it has no structure of its own, it formed a perfectly acceptable (to me) shape when packed with one firm bundle, a floppy cube, and some randomly tossed-in things.

Some advantages:

• Super light
• Looks smaller than it is, thanks to simple lines and compression straps
• Looks professional enough for me (I got the "bitter chocolate" version)
• Easily squashable, so fits in "full" bins

Disadvantages:

• No shoulder strap. I added lightweight D rings and a 7.5-oz shoulder strap.
• It's floppy if not full enough
• Easily squashable, so you need to protect breakables
• I would worry about it if for some reason I had to check it

It has tuckaway backpack straps that are unpadded but seemed comfortable enough during my very short test. I use it as a shoulder bag.

So far, I've brought it on regional jets when other passengers were told to gate check their bags. I also easily put it in an overhead bin when the flight attendants said all bins were full.

I'm minimalist packer, and the bag is a good size for me. I carry my laptop and ebook reader in a separate trim backpack. Both bags together will fit under the seat in front of me.

There are several reviews on Patagonia's site. I have a short review here, plus a photo comparing the duffel with my carryon-sized roll-on.