When developing REST APIs, HTTPClient is a great help for mac developers like me. It gives you the power of cURL and other libraries, but with a Mac GUI. You can set headers and params for PUT, GET, POST, HEAD and DELETE requests.
One of the problems I had were the Django error messages that were HTML formatted. HTTPClient only shows the source code, so I had a little trouble decoding those messages. Getting an optional WebKit View there was one of my ideas to first nail Cocoa and ObjC programming.
Looks like Steven Osborn already did that, and now everyone can enjoy those changes.