I think this will be useful for a lot of developers of iPhone/Adroid apps. Many don't have the know how (or time) to develop, run and maintain backend systems and it pushes the development cost way way up for clients and complicates our own applications.

We just integrated a purpose built CMS with a bunch of iPhone apps for a client and it was not a lot of fun so I'll give your product a try for sure.

As for feedback - the one thing with the UI is that having three different types of save buttons is a bit confusing at first but I'm not sure if there is a more efficient way to do it. Also, a big win would be if you added an etag along with the JSON with the location of the images to download. I do like very much that collections can be attached to multiple applications.

If your are ever in the Bay Area come by our weekly iPhone Meetup Monday nights in SF. (search iPhone in sf on meetup.com - our logo bleeds six colors...) or shoot me an email (profile)