Don't fix it if it ain't broken.
I should have thought about that when I saw an Eclipse update (turns out to be 4.4.0RC3) coming up when looking for a Force.com IDE upgrade. But I didn't. I went ahead with the installation. That's probably the old system admin version of me - always get the latest version!
Eclipse wouldn't launch, complaining about JVM 1.7 as required. Fine, I installed Java 7. It launched then, but I was greeted with a blank package explorer (after upgrading the workspace). Looks like the new version doesn't work with Force.com v29.
My mistake for trusting it aside, why would Eclipse push out a RC version? In the past I never had issues with Eclipse updates.
So stick with your original Luna - it worked fine for me. Just be prepared to reject any update they might put out there.