I don't think I understand this. To me a carry on is like the size of a backpack or bookbag. How do you get all your clothes in something like that? If it is a suitcase, where do you put it once you are on the plane??
Can you tell that I haven't flown very often??
Great question! Depending on the airline you're flying, you can bring pretty significant pieces of luggage right on board with you. For us, flying Airtran, we each have a rolling case that measures 24 x 14 x 13, which is actually 4" UNDER the maximum size allowed (55" for length + width + height). This size case will fit nicely in the overhead compartment on the plane, isn't too bulky, rolls easily down the aisle of the airplane, and is overall very manageable.
In addition to a carry-on bag like the one I mentioned above, you are ALSO allowed to bring a "personal item," such as a handbag, briefcase, or smaller backpack. We will each be bringing a small backpack in addition to the rolling case. In our backpacks, we'll put things like our OTC medications, camera equipment, snacks for the plane, a computer and accessories, maybe an extra pair of shoes or two that don't fit nicely into the rolling bags, and probably our toiletries. When we're not on the plane, the backpacks fit nicely right on top of the rolling bags with the handles extended, so there really isn't anything to carry. Just be sure to keep your bags with you at all times in the airport, especially if you have a layover!
One potential problem with the "nothing but carry-ons" method is the toiletries. I believe you're only allowed to bring liquids in 4 oz. containers or smaller, and that includes things like shampoo and other personal care products. Might have the same issue with OTC cough syrups, etc, so just be aware. We're packing travel sizes for all of those items, and we just use the toiletries provided by the resort.
As always, remember to check with your individual airline for their policies and size limitations on what you can bring onto the plane with you. You don't want to get to the airport and discover that you've got to come up with an unexpected $100 or so just so your luggage can fly with you!