From Omar Shahine's post mail.start.com we learn

Well, we launched Kahuna Milestone 3 (M3) yesterday with a new URL (http://mail.start.com). We are building Kahuna iteratively, and plan on releasing much goodness on a frequent basis. This is very different from the way that Hotmail and MSN has typically released software, but we feel it’s the best way to achieve success.

As I mentioned recently I've been using the Hotmail beta for a while now and it's a phenomenal improvement over the current version. Below is a screenshot of the beta in action.

If you'd like invites to the beta, you should keep an eye on the Hotmail team's space. You can also find more screenshots of the Hotmail beta on their space as well.