I spent the weekend modifying ObjectiveFlickr to work on the iPhone, which was mostly a matter of changing the response handling code that depends on NSXMLDocument. I was pretty much able to plug in my MCFlickrParser class, which I use in LOLCats, to create a NSDictionary structured very much like the XML document.
Yesterday I was informed about FlickrKit, which already works on the iPhone. FlickrKit seems more advanced, but it’s also a lot larger than ObjectiveFlickr. I created simple Flickr browsers using both frameworks. The FlickrKit version is 704k, while the ObjectiveFlickr version is only 148k. I’ve only tried it on the simulator and the performance seems about the same for both.
I will probably stick with OF for this project, since I would like to support Zooomr as well as Flickr and OF already seems to support Zooomr.
FWIW, FlickrKit should also work with Zoomr.
FK has all of the Flickr endpoint URLs inline, which would need to be changed. OF uses a dictionary of endpoints & you can specify whether to use Flickr, Zooomr, or 23hq (which I'm unfamiliar with) by simply setting a pointer to the endpoints.