We only do carry-ons (I don't mind doing laundry on vacation), and we each have 1 piece we got from Gander Mountain. They have the in-line skate wheels and pull handles, and a backpack that zips off the front. With the backpacks on, they wouldn't make it through the *ok* size of a carry on, so we zip them off right before boarding and wear our backpacks (you're each allowed 1 carry on and 1 personal bag, which is our backpacks), and the backpacks fit very nicely under the seat in front of us. Then as soon as we're off the plane, we zip the backpacks back on, so we're each just rolling 1 piece w/ nothing on our backs (in the hot florida sun!).
Not having to wait for luggage is really nice, and not worrying about airlines misplacing or damaging them is great too! We really have no problem fitting 4 or 5 days worth of stuff in these pieces, but we would have to ship home any big souveniors, which we never really buy anyway. It also really makes you not over pack, which I definitely tended to do our first few trips. Then I realized we all really never wore half of what we brought, so we pack way less now and it's so nice. I also always plan on buying 1 t-shirt or something each from wherever we go, so I plan that into my packing too. Also, the kids (ds6 and dd8) know they can't buy anything that won't fit in their luggage on the way home, so it really cuts down on the junk (but if something were that wonderful and they just had to have it, I'd ship it, but it hasn't happened yet).
The only time I can see this system probably won't work is when we go on our
disney cruise next summer. From what I read, there is so much you have to pack, I'll just suck it up and check some luggage, but I REALLY hate the thought of doing that anymore, now that we're used to only carry-on's.