Yeah, the backflip...does this actually have a use?
Well, aside from being perfect for dodging certain types of attacks (Dracula's double fireball), it actually has better height AND distance than the regular jump. There are some places you can get to and some little shortcuts you can take using the backflip to either cross long gaps or get your feet up somewhere a regular jump won't take you. There aren't too many of those places, and none are necessary, but it's a neat trick.
Also, the recovery time isn't too bad. It's just as fast to turn around and repeatedly backflip as it is to simply walk forward.
Also, you can whip while in a backflip, so it's great to dodge AND get in a free hit, or dodge and then wipe out some projectiles.