I love the interface, as it mostly works and in my opinion is much better than just about anything else currently available; including BlackBerry and Android phones.
The reason it's better has to do with the design of the user interface and the way it's controlled (android does pretty well, but is stuck a bit too much in older design concepts).
However I'm becoming more and more disgusted with Apple's goal of completely controlling the phone and all the content it gets. The recent move to kill iPhone apps that are competitive or are some how morally objectionable to someone at Apple (such as the recent decision to remove wifi finders from the app store), along with Apple's tendency to lock down anything they do in recent years is concerning me on a usability and moral level.
It only a matter of time before my disgust with Apple outweighs my desire to use the best device and I choose something else.
The question becomes what else there is. Android comes closest at the moment, but I'm not complete satisfied with that one ether.
Note: This image is not mine, and I don't know where it came from. If you know, let me know and I'll attribute it properly.