A while back I split some very lucky eBay lots with two friends of mine—they contained a swarm of OJR Zoids along with some Robostrux. I ended up with Battlesaurus, Brox, Giant Zrk, Terox...and Dimetrodon. Well, most of a Dimetrodon, after I passed on the parts someone else needed.
Its motor was dead, and its head had practically exploded in shipping. By "exploded", I mean snapped apart from the inside, leaving the sides of the face and eyes broken and the pilotman gone. I never did find him, and can only conclude he self-destructed. I gave up on the motor after taking it apart and making several failed attempts at getting it spinning—it remained throughly stuck despite all my jiggling of gears and leaving batteries in. To Dimetrodon's happiness and my puzzlement, the motor happily started up a few days later of its own accord. And so, after some waiting on boxes so Rant and I could gather proper Dimetrodon bits between our two incomplete Zoids, I set out armed with superglue, aiming to reassemble mine and find it some spare guns.
The first few portions of a Dimetrodon are a bit confusing sans instructions, photos, or other Dimetrodons, but I figured them out. The boxy flat piece that goes around the motor's spinny gear snaps onto the thingy that moves the head, then you pop the fins in and the tubes onto the sides...and the rest is just leg tail head stuff. Like Red Horn, Dimetrodon is a nice example of a simple design that works really well. It doesn't have any need for excess to do its thing, and it looks good once it's together.
If you've built a Dark Spiner, you've seen Dimetrodon's main gimmick before. To be honest, Dark Spiner does wavy fin much better, especially in its secondary "stare at the moving thing" mode. But Dimetrodon started the idea, and it's still pretty fun to watch.
The best bit about Dimetrodon's walk, to me, is actually its stomp: like Red Horn and Gul Tiger, it makes noise beyond its motor, slamming its little plastic feet down in an attempt at being menacing that works if you're the size of an ant or have a good imagination. My explodeytrodon's motor seems to still have issues, leading to one of its legs wobbling unhappily mis-step, but it still manages a creakily angry plod. Amusingly enough, the bum leg is the one I'm missing armor for—so it can be battle damage.
I definitely recommend Dimetrodon to fans of stompy things. So long as you don't expect Dark Spiner-level fin action, you'll be good, and it's seriously underrated. As of the time of me reposting this review, you can still find them for relatively cheap, which is rapidly becoming untrue of most of the NJR.
As to OJR versus NJR, they're both nice-looking critters...though the OJR (or an OER Spinefin) will set you back a lot more money. While the NJR is a bricky red and dark grey, OJR Dimetrodon is on the richer and slightly orange side of the Zenebas-y not-red-but-not-really-pink red. The other main difference is the eyes: NJR's are regular new Empire green, but OJR's are the same more olive-y green Storch has. Your other option is the Zoids2 Spinefin, which is forest green and silver chrome.
If you just like the design, grab the rerelease, enjoy the Fanbook Ex, and ponder the mysteriously purple caps.