I think I'm going to order the Logitech Driving Force EX from Walmart for $60. I see a number of eBay sellers selling the Driving Force Pro for not much more, but the EX weighs about half as much so I think it'll work better latched to my plastic McQueen & Mater TV tray.

Also the fact that it's much less bulky (no separate stick shift) means it'll be easier to store.
I see they're also selling a bundle of the Driving Force EX with Gran Turismo 5 Prologue for $89, which is a great deal, but I'm thinking that Prologue would be a waste of money since I'd probably want to get the full game next year.
We shall see. . .