My renewal went stunningly well...
I returned from London (UK) and landed in Orlando, FL en route to Detroit, MI. The Customs Agent noticed the CBP sticker in my passport and asked why I didn't use the Global Entry line instead. I explained that I had already scheduled the interview appointment for the upcoming next week or so (can't remember all of the details exactly, this was a while back) since I had been out of town on business.
He indicated that GE had an "Enrollment on Arrival" procedure at MCO - then closed the line to the booth, and then did the interview right there. I had my new card show up in the mail literally in a matter of days afterwards!
Totally awesome...