J.D.
We highly recommend a comletely separate, parallel install for Eclipse 3.0.2/MyEclipse 4.0M1 to ensure that it behaves as well as you need and does not disrupt your current working environment. That way, if you find a “fatal flaw”, you can simply drop back to the production release.
FYI: for future milestones and GA of 4.0, you’ll be able to update through the update site to keep trying the new releases.