Optimus Prime is alive, totally not a zombie and leader of the Autobots again! Hot Rod, Kup and Blurr have new toys! And the upcoming figures will practically be two Transformers in one! And they've got a fourth season to keep on advertising them!
What could possibly go wrong?
Cock-ups in production could appear, that's what.
It's written by David Wise, so that's not a problem, he's worked on Transformers before - problem arises when he's told to write a five-part story and then compress it into three parts. Still, with Optimus back surely that'll make up for everything, right? I mean, he only keels over from prophetic visions every five seconds and isn't actually seen shooting anyone. Nevertheless, it relies on the primary characters of season 3, so it's not like kids are going to be left confused when these new fellows march in. Instead, kids are going to be confused when these new characters march in and half of them don't even do anything. Of course, that's happened before (remember Windcharger?) so it won't effect much, ja?
There are nearly thirty new characters, if not more. And over half of these characters are heads and guns.
All this and it was unlikely that there was even going to be a fourth season anyway, so if axed, it had to provide a fitting conclusion to the whole series. That's what a sane man would call a tall order.
The Decepticons have been driven into hiding, but just when the Autobots least expect it (when talking about how gosh-darn peaceful it is without a Decepticon invasion) the Decepticons invade their territories and aim to use the power of the Plasma Energy Chamber to destroy a huge chunk of everything. That is thrown to the sidleines, however, when a number of Autobots and Decepticons end up on the planet Nebulos, where a similar feud of war and oppression is taking place, which inspires both sides to incorporate themselves with Headmasters and Targetmasters, doubling their firepower and brain power, as well as the number of guns shooting each other at the same time! Coupled with that, a convenient prophecy and Spike's dose of PARENT RAGE the Autobots reclaim Cybertron again, chase off the Decepticons again, and allow Cybertron to enter a new golden age - again!
It advertises the latest toys, has a minimum quota of Optimus Prime input and provides a satisfying conclusion while simultaneously allowing for a continuation, so it does all it needs to do. It shows all the characters, though naming or introducing them is often ignored, and to do all that while still remembering there's an actual plot involved... well, I'd have to say I commend David Wise for accomplishing it.
Doesn't actually make it a very enjoyable watch, though.
In Japan after season 3 this was their first opportunity to make a whole series with their own writers, and thus they got The Headmasters, which sadly doesn't have Brainstorm suing the Decepticons for stealing his idea, but it at least has time to develop the characters.
It's really, really hard to legitimately recommend watching this, though. I mean, it's a curiosity and nothing too painful, but it's not very memorable. Still, it may not be a good ending to the series, it's still an ending.