He may have some problems, but I love my MP-5. As far as the complaints that the fusion cannon is too big... That is true, but there is a (*cough* third-party *cough*) soloution for that, that also helps the alt-mode out a ton.
Mind you, as I said, he definitely has some problems. But he's still awesome. I'll take him over Hegemon with his (in my opinion) weak looking alt-mode and accessories (the stock extension) that seems to have no use with the robot mode any day.
That being said, since they've done a new Optimus, I'd not mind if they took another shot at Megatron in the new MP scale, as well. The legs could definitely use some work, perhaps with a transformation somewhat inspired by the Legends class version (more complexly designed to fill in the hollow back end, of course). But if they do do another MP Megatron, I suppose there's an even chance they may do a non-gun alt mode (such as a G2 tank) which I know has many advocates, but I am not one of them. We'll see, I suppose.
And until such a hypothetical day comes to pass, as I said I am more then happy with my MP-5!