I've been playing with Camtastic on my iPhone 3GS. It's a fun camera app that provides scene modes, film choices, sequence shooting, and a variety of self-timer options. Once you take a picture, it sends the image to the "lab" for processing (shown below). When the image is finishing processing (it doesn't take long), you can send the picture to your photo library on the iPhone, to Facebook, or via email.
Two different film processes just completed in the virtual darkroom.
This is a real workflow difference with Camtastic; it doesn't send images directly to your iPhone photo library, but holds them in the "darkroom" until you decide to move them along (or not). At first, I wasn't sure how I felt about this. But now I kind of like making the final decision.
The film options are interesting, and unlike what we're used to in the digital world, you have to wait a few seconds for the image to develop in the darkroom before you see the effect. In way, it brings back that bit of anticipation from the chemical days.
I didn't find the scene modes quite as useful, and left the camera in auto mode most of the time. But I did like the self-timer options (2, 5, 10, 15, & 30 seconds) and the sequence shooting choices (1, 2, 4, 6, & 8). The built-in electronic level is also quite handy for lining up your shot.
Camtastic is available in the iTunes App Store for $1.99. I'm keeping it on my iPhone.