Okay, I've been looking at code and poking around, looking for bugs and small holes and the like (my apologies to the gods for those who may noticed slightly odd things in the logs.
So here is what I've found...
Guest User is not locked out of the following superdocs:
Other than that, Guest User seems pretty much locked down, more or less.
N-Wing says: ok, did all those boring changes :)
In the sense of reusing writeup space, I'll add a couple of more here.
- Guest User (and other non-edev users) can get to the new scratch pad (you may want to patch that up)
- In the new /msg me section of a user's homenode, Guest User can see the form, even if it doesn't really do anything.