Great article about why open source projectsw are so UNusable for end-clients.
I think this ties in with why the great Web 2.0 software so far has been proprietary!
I also like the take on the value of interface design and wireframing:
Coding before design. Software tends to be much more usable if it is, at least roughly, designed before the code is written. The desired human interface for a program or feature may affect the data model, the choice of algorithms, the order in which operations are performed, the need for threading, the format for storing data on disk, and even the feature set of the program as a whole. But doing all that wireframing and prototyping seems boring, so a programmer often just starts coding — they’ll worry about the interface later.
http://mpt.net.nz/archive/2008/08/01/free-software-usability
