Is is because people don't like the extra size or because it looks like an Alien?

I've been thinking about getting a back-up body, and the motor drive bodies are so much cheaper than manual crank ones, I may just go with one of those, as it might actually be preferable for certain types of photography to have both.

Are they less reliable or what? I mean, its not exactly an insignificant price difference, i'm seeing about a $200-$300 price difference...