To juice things up, we are going to have a best user interface contest. All you have to do is nominate a web based software or service that you believe has the best user interface.
You have to explain what you like about it and what you think could be changed.
I nominate: 37Singals
Pros:
Their complete line of products are very user focused. Simple to use and straight to the point. I like that, there is not a lot of guess work involved.
Cons:
I wish some of their free apps had some more features.
Who do you nominate?