To continue on the Luke vs the AT-AT thing: When luke crashes and pulls his 2nd pilot out of the snowspeeder, it is crushed by the AT-AT. However, the AT-AT steps on it and that's about it. Considering the size and weight of the AT-AT the speeder should really be crushed, or at least pushed in the ground. Now it looks like the leg of the AT-AT isn't really having effect when it steps on it with his FULL weight.