Just to add data for people who'll have to send their 360 in for repair. The repair center received mine on the 7th, they send one back out to me on the 8th (should be here 13th). Anyway, a one day turnaround doesn't sound bad.
Edit: Well, it's delivered today on the 12th. So basically 18 days downtime for me. Replacement seems fine so far, just had reconnect and redo the HD-720p & audio settings. My old one was build in Oct/Nov-ish 05, the new one is build 3/23/06.