In reply to Tom.

Based on just reading its description and not actually testing it, it sounds like it would be a good solution for many cases. Two things stood out to me though:

1) Temporary users cannot delete other users. That's a major plus.

2) It allows site owners to assign any role to the temporary user. If that's the case, I would still couple it with a role/cap management plugin to make sure they are not accessing screens they shouldn't have access to.