If you’re using the Three20 library for your iPhone development and decide to upgrade to master (which works perfectly fine for me) you’ll need to update your project. If you update you’ll notice you’ll get tons and tons of errors, this is because Three20 decided to use a `modularized` build system. Ah, well fine. No where on the website or in the notes of the github repos they actually mention how to upgrade (at least not to my knowledge). After searching just about everywhere and reading quite some angry Three20 users post about how much three20 sucks (which I don’t think they do!) I found a github page on how to update.
So for everyone that wants to upgrade to the new Three20-module-style-thing; here’s how to do it http://github.com/facebook/three20/blob/master/Articles/AboutModules.mdown
Hope that helps :)