World of Goo has moved an impressive 125,000 copies. With the price ranging form $5 to $10 in that time, that's a lot of scratch (and a whole lot of goo).
To put things in perspective, the 2D Boy site notes that the best 31-day sales period for the WiiWare version was 68,000 copies, while the best for the Steam version was 97K. The developer adds, "So far, the iPad version is by far the fastest selling version of the game, both in terms of number of units sold and in revenue generated."
Check out the 2D Boy site for an extensive analysis of the iPad launch -- with charts and graphs! -- and an inside look at the indie development scene.