Jon,
Best investment I made was to purchase a Hartmann rolling hanging bag (41in. Mobile Traveler Garment Bag). I got it at the outlet store so the price was much cheaper that at a luggage store 600 vs. 300. Why is it such a bonus? It fits perfectly in the overhead compartment, (CO's at least) has wheels and an extending handle for other bags/briefcase, will hold suits, shirts, in the hanging bag and has internal and external compartments for t-shirts etc...
The caution I will give you is that large carry-on bags work well if 1) you are elite and get to board first (Plenty of overhead space) and 2) you are not prevented by the airline from bringing it on-board (cutouts on the X-rays).
Early boarding is a wonderful benefit for getting overhead space. This bag also works very well as checked luggage, I had to find that out a number of times too.

As an added endorsement, after letting them borrow it now my Mom, Dad, Finacee and Brother have all dropped hints about what they want for their Birthdays... my bag.

BSL

PS. Get at good bag, if you are going to be traveling you will get your money's worth out of the ease of use and the warranty WHEN it gets damaged.