Hey all,
I'm also an iPhone developer and I've been working on another drawing app called NetSketch. The official 2.0 release of the iPhone will allow you to install apps without jailbreaking the device. It seems like there will be quite a few drawing programs to choose from (though I admit I'm biased).
So if you're thinking about jailbreaking your device - dont! There will be plenty of options soon 
- Ben Gotow
http://www.gotow.net/