Beast Machines was the sequel series to Beast Wars, that in itself was a sequel to the original 80s Transformers cartoon (not that it meant to, originally, but when you mention a 'great war' in the first episode, people are going to assume things).
Beast Wars was pretty much universally loved. The episode 'Code of Hero' is a shining example of how fantastic cartoon storytelling can be, given half a chance. People, understandably, were excited when Beast Machines arrived. It was set on Cybertron! With vehicle Transformers! And...
And some really weird hippy stuff.
I'd heard Beast Machines wasn't great, and so, not wanting my love of Beast Wars ruined by what came later, I never watched it. Until this summer. This summer I finally sat down and gave Beast Machines a chance.
There are some great things about the series. The writers (a new team, replacing the writers from Beast Wars) were able to plot out a story arc over the whole series, so it's nicely paced. Shame it isn't a particularly great story.
Optimus was always a bit of an optimistic dreamer in Beast Wars, but he goes completely crazy in Beast Machines. He's turned into some kind of religious nut, wanting to meld the organic and mechanical on Cybertron. It all gets very preachy and very annoying.
There's a big change to Rattrap, who, in addition to now looking like a small boy, suddenly has super computer skills. With Rhinox gone, I suppose they needed someone to take over this technical role, but Rattrap?
All the robots have new modes, obviously, as Hasbro wanted to sell a bunch of new toys. There are two problems with this. Firstly, since the series and the toys were developed separately the two don't have too much in common, and secondly, the designs are all a bit crap.
Sorry, Designers, but I think they all look terrible, and few look anything like their old Beast Wars designs.
It's a very dark series, both tonally and visually, and 'dark' doesn't always mean 'good'. The philosophical aspects are likely to go right over the heads of the target (child) audience, and even as an adult watching they just bored me. Making your lead character annoying was a bad move. Optimus should be the star of the show, not the one you hate the most.
And as for what they did to Rhinox...
I don't regret sitting through all 26 episodes this summer, but I'd certainly have had a more fun time watching Beast Wars instead. By all means watch Beast Machines once for curiosity, but I really doubt you'll do so again. I know I won't.