I have one similar in size to this one (20x14x9):
http://www.amazon.com/Travelpro-Luggage-Maxlite-Expandable-Spinner/dp/B007BY2GPU/ref=cts_ap_2_cts

Mine is made by Atlantic and is a bit smaller, 18x14x9 (that's the bag size - if you count the wheels it's more like 19x14x9). And mine only has two wheels, so you have to tilt it to roll it. The newer ones all seem to have four wheels so you can spin and twist them every-which-way.

I bought this size specifically because it fits under the seat on a 737. So if all the overheads are full from the fools that drag ridiculously huge things onboard, I can still get mine under the seat. I do not have to check it due to the inconsiderate others who carryon everything including the kitchen sink and fill up all the overheads.

I don't normally carry suits, but when I have they've come out of this little bag just fine. I turn them inside-out and fold carefully.

My biggest criteria for a carryon is that it MUST fit under a seat. That way I'm not at the mercy of the rude overhead bin hogs. If there's room, I'll put it in the overhead. But on every flight I've taken recently, the bin hogs never leave any room.

I have a Kelty Redwing 44 backpack that I wanted to take on my last trip, but I didn't. While that pack would fit in an overhead, I highly doubt it would fit under a seat. So it got left at home in favor of my "I know it will fit" bag. When I have to take a laptop, that goes in my little bag too. No seperate laptop bag. One and only one carryon for me. I do not like to be forced to check bags - period.