I've noticed that if you have installed firmware 3.1 (or later) on your device and you are using Sprite (not AtlasSprite) the performance will increase between 5% ~ 30%.
If you compare the v0.8.2 performance-test (firmware 3.1.2) vs. v0.8.1 performance-test (firmware 3.0) you will notice a nice performance boost in columns 1,5 and 9.
This performance boost is not related to cocos2d changes, but to firmware changes (cocos2d v0.8.1 on firmware 3.1 runs at the same speed as v0.8.2 on firmware 3.1)
v0.8.2 perf tests:
http://www.cocos2d-iphone.org/wiki/doku.php/perf_test:0_8_2
v0.8.1 perf tests:
http://www.cocos2d-iphone.org/wiki/doku.php/perf_test:0_8_1
For example in firmware 3.0, test E9 runs at 31 FPS, while on firmware 3.1, the same test runs at 41 FPS.
I don't know why this is happening, but it is good news.
