I personally like the Energon Megs design... sorta an SR-71 from hell.  Works for me.  Personally tho, I think Megs should be a triplechanger tank/jet.  I personally hope the movie Megatron personality is nothing like the G1 personality.  I recently watched the first season, and Megatron was annoying and stupid.  I much prefer the later incarnations of Megatron where he's actually a strategist and actually does evil, rather than just laugh maniacally and whimper when the Autobots shoot at him once.
I realize the one and only point to the Transformers is to sell toys, but at least give us a Megatron with the castiron manifolds to wreck havok on the population of earth.