The problem with the movie Megatrons is that you don't intuitively know what the alt modes should look like. They transform from robots into... umm... some thing that flies, and then some thing that rolls. As tricky as ROTF Leader Optimus Prime may be, at least you instinctively know what the alt mode should look like and what you're trying to achieve. Megatron's alt modes are just so damn weird^abstract-fantasy-based that it's hard to intuitively know what you're trying to achieve.

This is why I prefer DOTM Voyager Megatron over TF1 and ROTF Leader Megatrons... he transforms into a truck... I know what the alt mode should look like and it makes it a helluva lot easier to get there. With TF1 and ROTF Megatrons, once you finish the transformations, let's face it - you only know it's correct because the instructions say so.

DOTM Megatron - from truck to robot and back!
TF1/ROTF Megatron - from mangled-robot to robot and back!