Reading this "Top 10 Application-Design Mistakes" we can make good construstive self-criticism.

So, I'm writting down some of the main ideas taken from Nielsen for not forget:

• Base the decisions on user research.
• Don't just implement feature requests from "user representatives" or "business analysts."...Requirement specifications are always wrong.

Basically, as he says: applications fail because they (a) solve the wrong problem, (b) have the wrong features for the right problem, or (c) make the right features too complicated for users to understand.

Via Olga Carreras' Blog.