The Command spell now restricts you to a fixed list of commands. I think this is a terrible change, as creative uses of spells is one of the great things about D&D. I think they did this just to make it more easily adapted for Project Sigil.
Animate Objects changed, too, in a similar creativity-sucking way. Now you can't animate objects fastened to a surface, and no gargantuan objects. Nothing flies anymore - all targets grow legs. You get a number of points equal to your spellcasting modifier, with bigger objects taking more points, so you can animate medium/small (1 point, 10hp, 1d4+3 damage), Large (2 points, 20hp, 2d6+3+mod damage) or Huge (3 points, 40 hp, 2d12+3+mod damage) objects.