I've never participated in a hackathon before, and didn't know what to expect.
I met three developers at the start, and within two hours we started to build Keepsake - an app that enables families to capture and share text, pictures and video. In 50 hours we built a Windows Phone App and Windows Store App tied together through Azure (Blob storage, Azure SQL, Web Roles, and Mobile Services). Clint's hackathon crew was top-notch, and I learned a ton from them.
The hackaton was one of the most challenging things I've thrown myself into in long time, and it's one of the most rewarding experiences I've had. Can't wait for next year!