I don't have the switch engine option either. I have uninstalled, reinstalled, rebooted and taken the battery out and restarted and every combination thereof. I am pretty sure that the new browser is installed (as some pages render differently), I just don't have the option of toggling to the old rendering engine. I am running the most recent firmware and restored my data from previous backup.

Some problems I am noticing:
-map tiles not appearing in google maps
-www.escapepod.org title image only partially loads
-If I have flash turned on, the above page crashes (which was the same with just Opera install).