we have the latest FIM R2 SP1 installed and configured in our environment.
Unfortunatelly, we still experience following "performance issue", which we also had in FIM 2010.
The initial requests against the FIM Portal takes several seconds. After the initial request the portal response ultimatelty to the requests.
This happens the first time and is faster once you "active in the page", but if you leave the page then return 2 minutes later...its again very slow for the first request.