Ribbons :)
Excellent App. I plan to use it in my classes and meeting with students. I see that there are plans in the works for the next update to include views other than ball/stick. Excellent! It would make this app much more useful to toggle ribbon diagrams to be able to better understand the structures, organization, and motifs.
Bravo!
I've been developing Avogadro, which is primarily an open source molecule builder. Some friends jokingly tried to get me to make Avogadro for iPhone, so I'm glad you did it first. :-)
http://avogadro.openmolecules.net/
I'd be glad to help share some code with you. Granted, Avogadro works because it has some huge code libraries, but we can definitely help with code for representations.
Send me an e-mail if you have a chance. I'm sure you're swamped, but I'd love to talk briefly about science and software.
Thanks for the kind words. Let me know how effective it is in a class setting. With a free iPod Touch being given away for every educational purchase of a Mac this summer and with the lower (up-front) price of the iPhone, there will be a lot of compatible devices in the hands of students this fall.
I think that spacefilling and cylinder representations will be next, as those should be reasonably straightforward to implement. The calculations to generate 3-D ribbons are a bit more involved, but there is code out there and I've had at least one offer of help on that front. From the number of requests via email, iTunes reviews, and here, I've moved it higher on my list of future improvements.