The original Masterpiece Optimus Prime is nearing a decade old, released in 2004 as "20th Anniversary Prime."  And since this is Optimus Prime, it's no surprise TakaraTomy's come back again after all this time to do it again.  .... but maybe a little smaller, yes?  The first MP Prime was... kind of huge.  He was clearly designed to be a stand-alone item, without thought to "oh hey i guess maybe we should do some other guys to go with him," forgetting, uh, maybe not everyone wants a range of folks-who-aren't-Optimus-Prime at that huge-ass scale.

So this new MP Prime is smaller, but not dinky by any rate.  He's got some die-cast in him, so he's got a good heft -- but not so much heft that he's constantly in danger of falling over, like the old one was.  The ankles on this guy don't have to support nearly as much.  And New MP Prime has a different transformation and some retooled proportions.  He makes the Old MP Prime look like My Buddy and/or Kid Sister.

(I really need to throw my old MP Prime up on eBay, but I can't find any accessories other than the Energon Axe.  No Matrix, no ion cannon, no nothin'.  Knew I shouldn't have let Zombie Tarantulas keep MP Prime's Matrix for eight years.  Dude totally ganked it.)

New MP Prime does some of the things the old one did, but not all.  His chest doors still open up to reveal the Matrix, of course, and you can still pry it out of there.  He doesn't have some of the smaller things, though.  There's no more wrist communicators in his arms, his mouthplate doesn't do the talky-talky thing, nor do the flaps on the fronts of his legs flare when he steps.  However, his transformation does make room for Spike Witwicky (who's included) to sit inside while Prime's in truck mode.  And, oh my lord,  his truck mode actually has side-view mirrors.  They managed a way to get those to exist.  It makes me happy.

I also like the new range of motion for his head.  It's articulated at the neck plus the neck itself can rotate back and forth, allowing Prime to look up into the air or into his own collarbone.  His fingers are articulated, with a joint at the knuckles for his pinky/ring/middle fingers and one at the knuckles and mid-finger for his index finger.  I do wish his elbows and knees were double-jointed so they could bend over on themselves.  He can't do the Kneeling Big Nooooooo!, which is a tragedy.

TakaraTomy also decided that his legs should awkwardly conceal his leg-wheels, since those disappeared during transformation in the cartoon.  Well, their execution looks dippy, and I like seeing his wheels there, so I've been leaving the concealing flap folded back against the rear of his legs.

Since this Prime is smaller, it's not nearly as incredible an ordeal to give him a trailer.   The Old MP Prime got a trailer (eventually) in Japan, and I bet that thing is stupidly huge.  This one is just small enough to survive the transition to American toy shelves.  Even so, the packaging is still pretty huge.  Grabbing it off the shelf and carrying it to the check-out counter is like toting a giant stereo boombox.  Also, hey, you're going to have to completely tear apart the packaging to get the instructions out.  They buried that sucker deep in the bowels of this thing.  Like the tell-tale heart, the instructions are hidden under the floorboards.

Generally I'm fine when Primes don't have trailers.  The original trailer is just a box.  A box that takes up space.  Looooots of space.  It's a waste of mass.  But I don't absolutely hate this trailer.  For one thing, it hides the back of Optimus Prime's truck mode, which is obviously a pair of robot legs and not the back of an actual truck.  It also does all of the things the original 1984 trailer did, like open into a battlestation or repair bay.  Roller is included, who can also tow the trailer himself if he wants to, while Spike drives.  Unlike the original trailer, this one has spots to stow all of Optimus Prime's extra stuff.  You can nestle his axe and gun in their intended spots.  (The gun also folds in half and stores in Optimus Prime's back as first seen in the Dreamwave comics.  Thanks, Pat Lee.)

If you like Optimus Prime, he's a pretty good thing to have.  He's exclusive to Toys"R"Us, though.  Hopefully his $100 price tag ('cuz of the huge trailer, you see) will mean he won't disappear off the shelves quicker-than-the-eye.

I have some additional photos on my Tumblr.