I've spent a few days running Idea (Selena 7.0.3) on the newly released Apple JDK 1.6, but in the end I've switched back to 1.5.
The main issues are a lot of slowdowns, and occasional deadlocks (especially with multiple windows open).
I've logged a Jira issue with my comments at http://jetbrains.net/jira/browse/IDEA-18049
I've heard from one other who was experiencing kernel panics with Idea on the new JDK when starting a debug session.
What are your experiences with the new Apple JDK and Idea?