Installed the new Team Development For Sitecore 5.5 today. The new feature for auto deploying content files is something I've been needing for a long time. It cuts development time when working on CSS, Javascript and even cshtml changes by 1000%. This will allow me to see my changes much faster and has a direct impact on development time.
There are quite a few other features I'm looking forward to experiencing, especially the new Delta builds.