I tried installing mojoPortal this morning on MySQL and ran into an issue where an error would be thrown stating that the mp_taskqueue table doesn't exist. Of course it didn't exist because the Setup routine hadn't run yet. After some head scratching I figured out the problem was I had already set the UseAppKeepAlive and AppKeepAliveUrl values in my user.config (I do this on a lot my installations because my customers tend to be small and they don't generate a lot of traffic). When I set these values and then run setup against MSSQL, I don't get any errors.
I can easily remind myself that I need to comment those settings out before running setup on a site that will be using MySQL but I figured I would bring it up just in case it is an easy fix.
-Joe