An extra body in practice is always a good thing, especially if the player is a hard worker. I can only guess about Allen's work ethic, not seeing practice, but from I remember being impressed reading articles in St. Louis papers, not just buy his athletic ability but his dedication/character.
His attitude seems great. He doesn't seem too concerned about his minutes, more about the team. Bga is right, having a guy that the team all seems to like at the end of the bench can only help, especially when that guy seems passionate about the team. And of course, he isn't costing us a scholarship. His high school days tell us he is talented, and if that talented ends up amounting to zip, we still ended up with a guy on the bench contributing some small positive things at no cost.