I use IDEA for my primary IDE and Eclipse for Clover (at this time we only have licenses for the Eclipse plugin).
I am trying out the IDEA 10 Evaluation, since we use TFS 2010. I'm seeing some bugginess, but the biggest problem that I'm seeing is that if I update a file in Eclipse, that IDEA seems to lock up and never recover. I have to kill the task in Task Manager.
In IDEA 9, this worked just fine and IDEA picked up any file changes immediately and properly refreshed the file. This appears to a regression in IDEA 10.