I got my yesterday from AmiAmi and by god WHAT A MASTERPIECE.
Seriously this thing is like the Magnum Opus of the masterpiece line. As a generally critical person I'm genuinely struggling to find fault with MP-39. I'm amazed at the sheer quantity of gimmickry they've pulled off without affecting the alt or robot modes of this figure. It's a true masterpiece of engineering. I'm actually glad they took their time with this guy (so long after his bro Sideswipe) to get him right.
For once I'm actually quite satisfied with what I have received for what I paid. If I had to recommend one Masterpiece figure over all others it would have to be MP-39.