iWin is selling it for $14.99, too, though no multiplayer.
Gamehouse has it for $9.99. Again, no multiplayer.
So go Steam if you want multiplayer and Big Fish if you want the campaign for cheap.
Yeah, I guess Puzzle Quest, Plants Vs. Zombies, World Of Goo, Peggle, Mystery Case Files, Fairway Golf etc all suck then... let's all play Diner Dash....ugh...