We started after launch a task that I estimated as taking roughly three days. we were finished by 17:45, all the way from the (fairly complex) UI to the back end handling and its interaction with the UI, the database, etc. In the end, it was a very smooth experience, and a really good feedback about the investment we made in frameworks and the code structure.
Hell, when we went out to coffee break, we realized that we structured the model all wrong, and we had to change a significant part of that. We still finished in four hours a three days task. I am fairly accurate in my estimates, so that was a big surprise. Then again, we actually spent the morning by going to production live, so we have a mature base to move on.
And on the way home a co-worker calls me and asks me about Ruby on Rails and MonoRail. He will probably be using that for the next project :-)