Hi everybody, we launched a iphone game "Dungeons and Coin" last month:
http://itunes.apple.com/us/app/dungeons-and-coin/id383084962?mt=8#
This project is quite successful in East-Asia Markets (Japan #1 Puzzle, # Free App in HK etc..).
We tested 3 free physic engine (ODE, Bullet and Netwon) in iphone and find that the best one (performance and accuracy ) is Newton.
Finally we decided to use it for Dungeons and Coin and the coming project.
The cpu power of the old iphone (2G,3G) and ipod (1G,2G) is very low but Newton still performance OK,
as other engines is basically no way to handle hundreds object in the scene and still in "interactive" frame-rate in old ipod.
And this game is free, try to download it and let you know the power of Newton in iphone
ps : here is the youtube video