Descriptive form status/error messages.

I think it would help you guys and your users to have more descriptive error messages in your forms. For one I just did a little test signing up for a new account using a known duplicate user name, and all it does is take me to the Ack! page. I'm sure a lot of people are ending up here when creating a new account. In that case a simple, "That user name is already taken." would suffice.