This is a fun little PDF that every DM should pick up! I would happily pay for a much-expanded version of "useless" spells.
Some of these seem a little powerful, particularly Rainbow Bridge -- allowing entire parties to walk right over any body of water at 1st level seems like maybe a bit much. However, it's easy for a concerned DM to tinker and say that it only lasts for, say, one round, or change it to a fourth-level spell. (Water Walk is a third-level spell and seems comparable.)
Some of the schools also seem a little off, like Grow Giant Hands. I'd see that as more of a transmutation spell than conjuration.
However, these are tiny nits to pick for such a delightful document! Kudos to Michael Klamerus for coming up with something so fun! I hope we get to see more in the future.