Unrevoked is now reporting that the Revolutionary tool, which is still in a developer preview, now supports the EVO 4G HBOOT version 2.16.0001, which has, until now, been virtually unbreakable.
As always, you'll want to read all of the instructions very carefully at the Revolutionary site before attempting to root your EVO 4G, and you are responsible for any potential damage that you do to your phone. That being said, the process is relatively easy, safe, and (dare I say) foolproof. Still, if you think you need a little hand-holding, check out our new EVO Gingerbread root tutorial.
[Unrevoked]Thanks, Ronald and Jim!