The main problem that I have with web services is designing forms. I hate design work.
I haven't yet found a good way to be able to just code and have forms for user interaction generated automatically, without using an overblown framework that tries to abstract the whole thing with MVC, forcing you to jam your logic into their structure and using their database abstraction instead of giving direct access to these kinds of things. I have in mind to get a web version of catgod, maybe I'll find something for it.