Is D3 worth the $55 upgrade from D2?

[Nethog]

Again thanks for all of your excellent feedback, particularly on the vanilla version of the game, the manual, D3 new features, and Shrapnel sale events. As for the $55 price, presumably Shrapnel has done their D3 marketing research and can make more profit selling say 100 games a month for $55, and figure they can't sell say 300 games a month for $30.