When the rumors of a Dell phone came out, I thought it was one of the dumbest things I'd heard. Now, it seems they are actually planning a whole series out of the gate, and not just variations on a single platform. The strategy seems like desperation - they don't know what the public wants, so they will make everything they can think of. (They don't need them all to be successful, just one.)
That said, I am actually really impressed with the case designs. These are very attractive, and probably the most likely iPhone contenders I've seen. I'd worry that the diversity in the product line will lead to poor focus and execution, and that none are truly great phones.