Surprised there aren't more reviews here of this little beauty but I digress.
I'm extremely satisfied with MP-09. Having heard there were some QC concerns with it, I decided to take extra precautions by using the instructions. I found them not to be that great in hindsight. I tend to prefer treating the transformation in two parts for the car mode: lower body followed by upper body. The legs are the hardest part and can be frustrating but after a few gos, you have a sense of where everything belongs. The biggest surprise in the transformation is realising that front of the truck mode is a facade completely unrelated to Rodimus. I was very shocked to find that as I had assumed the car would slot in nicely with a few adjustments. The wheels touching the ground I have found is a bigger problem with Rodimus Prime than it is Hot Rod. It will roll but not all the wheels will roll simultaneously, only some. Overall, the transformations are fiddly but oddly satisfying b/c it is a bit of a challenge.
I really like the overall feel of the figure. Aesthetically all of it's modes are extremely pleasing. If you look around the whole figure, it feels so wholesome as opposed to many standard figures where if you look at back view or side view, you see a lot of unused space that makes the figure feel incomplete. The transformation of Hot Rod to Rodimus is so simple but it works so well. If you're told changing the face, extending the legs a little and adjusting the spoiler is enough to convey the difference, you'd be surprised. They are very different figures.
Articulation is excellent as well. My only gripes are the shoulders are encumbered when rotating them backwards angularly.
Balance though isn't good. . I've found it hard to get him into a pose without toppling over. I would love a stand for this. It looks so good in so many poses but getting it to stay upright is the problem. If anyone could recommend a stand, I'm all ears.
My biggest gripe is the guns. They do not fit snugly at all. You can get him to hold both but it's a bloody chore. In Hot Rod mode, my advice is do not try to force the hands around the guns tightly. Just wrap them gently around. However, be prepared for them to fall out the moment you try to repose the figure. That to me is a no-no. In Rodimus Prime mode, it's much worse as the combined gun (as nice as it is) is just too heavy and the wrists give easily. That means you end up with a floppy weapon unfortunately. I'm hoping someone, somewhere just makes new fists that these slot better into. I'd grab that.
The trailer is good at what it does but really it's just a beefed up version of the G1 one. Very nice and gives a good platform of Hot Rod but it is simplistic. Would've liked the monitor/targeting screen on it to have some colour because it is a tad bit dull.
Overall I rate MP-09. Relative to the price point of MP-08 which I believe was similar, you get plenty more complexity and playability plus the trailer.