I did the bacon game jam last weekend using cocos2d-x. design and implementation start to finish in 48 hours. It was my first time and it was a blast. I underestimated how easy it is to use cocos2d-x for prototyping, and in retrospect I could have been more ambitious with design. It was okay though, it meant I could try shaders. Compiled to mac/linux/windows/android at http://bacongamejam.org/jams/bacongamejam-05/66/
Source also on the page.
Also wrote a blog talking about what it was like using cocos2d-x for a short term jam.