I think many people don't/didn't and probably will never understand this show, but I'd like to think that I do...so I'll try to review it the best way I can.
Beast Machines shows viewers the next step in Transformer evolution, where the only way the species is able to survive is a happy medium of a technological and biological mix. Many Tranformers fans thought of this as 'blasphemy' to the essence of what Transformers represents. I however, as an original viewer AND a lover of the Beast Wars series found this show great. It's the perfect getaway from an all-robot show and a 'natural' progression of what I do consider/think to be necessary for these beings to evolve and survive. As human beings, we're slowly evolving toward the technological - and though we're only talking about a show here, I think it's only logical that technological beings evolve toward the biological. The show however wasn't well received for 2 reasons - 1. kids didn't understand it. That is, the audience to which the show was marketed simply didn't understand the show, as it is a bit on the complex end. 2. fans didn't respect it. As I mentioned before, most TF fans want robots made of metal.
All in all, I believed it to be a great show and there are many like me who would have loved Hasbro to keep the series going, however we're a niche market - a tiny nook into the audience required to keep this sort of endeavor going. I'd highly suggest those of you who have recently gotten 'into' TF to sit down and watch Beast Wars and then Beast Machines, especially if you're a little more open minded to the TF universe. As for those who are hardcore "TF are machines! fans" - I'd suggest to re-evaluate these series. Watch Beast Wars, take it in, enjoy it and then move on to Beast Machines. You may feel differently.