I'm on F1 until Jul 2012. Right now on post completion OPT (01-May 2011 to 01-May 2012, technically can be extended for 17 more months).
Old Employer -- Last date: 17th June .. was on OPT
New job with new employer from 20th June 2011.
Previous employer filed H1 and it was approved(to be implemented from October 2011) after I left them (17th June 2011).
I opted to stay on F1 since I was on OPT, previous employer requested a revoke/withdrawal sent me email confirmation that it was withdrawn.