The really good thing about having back to back episodes is not having to wait a week for a story arc to play itself out. Mandy Moore gets the patented Scrubs Celebrity Fan Blower Treatment and between this and her guest arc on Entourage has proven herself to be a good sport about stuff like this.
Although they seem to be making J.D. goofier than normal this season even by Goofy J.D. Standards.
It came down to the 11th hour, but both Variety and Hollywood Reporter's websites are saying that BL has been picked up for a 5th season. I think the negotiations had to do with ABC buying out "Life on Mars" from David E.