So, the issue-xF is constantly "logging me out" while I'm trying to work with it, usually while trying to work with things like rebuilding the caches after installing an addon, or while importing data. (and then if I don't login, I then get a 'not allowed' or 'not found' (which I assume means that the fastcgi interface didn't report back, maybe XF crashed?)
My instinct is telling me that this is is actually something triggering a timeout, or possibly something going wonky with the fastcgi interface running the PHP. Their nginx<--->fastcgi interface does has a nonmodifiable 60 second limit, so might there be something to tweak with that?
Also as an aside, their config comes with apc by default, which I have disabled with a mini php.ini in the home directory.
All this is up at forums-phoenixrising.dotcloud.com.....if anyone wants to dig further, I can give access.