While I can't say I agree with the entire list, I submitted the link to start a discussion on interface design. Usability, or the "user experience" as I like to think of it, is the most important aspect of an application in my mind. It determines whether people will be quick to adopt your offering or even try it out at all. I'm actually a big fan of rich Internet applications, but I see "richness" applied too liberally in places where simplicity would have been preferable. I've been spending some time reading about human-computer interaction, and it's a fascinating field.
danielha - yeah, i think casting something quickly and have something to start with is far better than use a lot of time thinking for a grand scheme but to later on find out users won't bite to it.