I'd say that a 26" is the best general-use case for checking, especially if you want to pack for several people in one bag for domestic trips.
That said, 29's are still useful for certain types of travel, and I bought one after the 62" restriction went into effect. It replaces my 31" Samsonite Ultralite EZCart, which I *loved*. The 29" is actually much heavier than my 31" was, but it's still a good 4-wheel case. I use it for long overseas trips with kiddies in winter, when I need to pull my luggage around while walking through cities. I find that it is much easier to navigate public transit with ONE rolling bag, even if it is large. It does go overweight, but I just use space bags and a duffel, split the contents before checking it, then put the excess back after I claim the bag at my destination. The most I've ever put in it was 90 lbs., but it rolls beautifully at that weight.
FWIW, the 29" Samsonite Oyster Cartwheel is the most popular suitcase in the world. (It also comes in a 26".) They are cheap, strong, lightweight, and colorful enough to find on even the most chaotic carousel. They even sell them at the left-luggage counter at Heathrow, for situations when the airlines refuse to take someone's really beat up tied-with-string pressboard trunk. This is an Oyster Cartwheel:
http://us.samsonite.com/webapp/us/s...72&storeId=10001&langId=-1&keyword=oyster&pc=
They are not exactly luxe, and personally I prefer a modern extension handle, but they have a really dedicated following, especially among folks who must fly a lot in the third world.