The All-in-Wonders are nice if you're looking for a powerful 3D card and a TV tuner all in one package, but they are expensive. For the price of a Radeon 9700 Pro All-in-Wonder ($365 on Newegg) you could get a Radeon 9700 Pro ($292) and a Leadtek TV2000XP ($51 and a great card) and have $22 left over. Plus a lot of people don't have the money for the top of the line cards from ATi and unfortunately ATi only manufacturers the All-in-Wonders with their top of the line models, so that makes the price even harder to swallow.
I've never had the opportunity to play with the TV features on an All-in-Wonder, but I used to have a TV Wonder VE and it absolutely sucked, horrible driver support and buggy as hell.