Here's my story. I had stock 2.2.2 and rooted it via Gingerbreak 1.2. Then when I discovered that 2.3.4 was available for the phoenix, I unrooted (again via Gingerbreak 1.2), uninstalled the existing version of Superuser.apk, gained temporary root via ADB, and then completed the process using the instructions below...
This is obviously not the cleanest method, but I could not get SuperOneClick to cooperate.
Anyway, it's rooted and working great thus far: Titanium Backup just finished backing up all my apps and data without complaining.