It's similar to SizeUp and Cinch, but allows for quite a few more options. You can assign one window 33% of the screen and another 66% of the screen, and tons more. And you can make presets.
Seems like the perfect option for 30" monitors. You lucky dog...
1. Laptop screen becomes secondary screen for programs in the background like email or Spotify or Winamp. Things I want keep open with relatively quick access but not in my face.
2. Multiple visible windows on the same screen, and on both screens. This is useful in way too many situations and a serious productivity boost.
http://irradiatedsoftware.com/sizeup/
Cinch, by the same author, is also good. You don't need both.
But if I were to get a 30", I would also get a 22" display - rotated vertically, they are the same size.