I take Fly on almost all of my characters, because it's fun, cool, and easy to use. Yes, it's slower than the other travel powers, but I don't care about that. When I don't take Fly, I take Super Jump. I hate Super Speed, because I hate running into things like a hyperactive squirrel on crack without vertical control. I don't take both SJ and SS, because why waste a power selection on two travel powers, when one will usually do (either Fly or SJ)?