If you think XML is too complex and has too much overhead for your needs, or simply your backend does not support it, then you should check out a JSON parser.
Here is a good tutorial with parsing some Flickr JSON messages:
The JSON parser used in the tutorial, can be obtained freely from here:
A faster JSON parser is also available with same functionality: YAJL
(Be sure to download the YAJLiOS framework when clicking the Download on GitHub site)
XML is a widely used format, even in the mobile world, where t became the standard for communicating between device and web server or web service.
There are plenty of parsers out there, here is a good comparison about them:
I have tested out TBXML, which has very good results in reading and parsing, however XML writing and creation is not supported.