Just to clarify updating a rooted phone.
JUST rooting (no custom ROM installed) works fine and you don't need to change back to a stock image. However, you will loose root access to the phone. I haven't had a chance to try re-rooting again yet (need to do it on my WinXP computer at work). Sounds like you can still root the phone with the same method from what I've been reading, though. Will confirm tomorrow.
However, if you've got a custom ROM installed, you will need to change back to a stock image before running the update. But, if you're running a stock image and aren't interested in any of the fixes done by this patch, there's no need to do anything. Just wait for your custom ROM provider to give you an updated image.