I didn't like Dreamwave's G1 series when it first came out. Volume 1 was a rather dry "rock 'em sock 'em robots" (makes Revenge of the Fallen look like a literary masterpiece by comparison :/) -- but the story did improve after Volume 2. Editting was kinda sloppy, but the series had potential, as did several of the G1 spin-off stories, like The War Within/Dark Ages, Micromasters etc. -- I felt that Dreamwave's G1 series got cancelled just as it was getting good.
I personally didn't enjoy Energon as much as Armada, but again, it might've been awesome had it been allowed to finish to its conclusion (cos most of the best stuff in Armada (e.g. Worlds Collide Saga) happened in the later issues). And yeah, the abrupt cliffhanger ending did suck. The fact that it was so suddenly cancelled and the creative team didn't have a chance to try to quickly tie the story up and conclude it really hurt.
A lot of us complain about the way that other Transformer stories have been hastily concluded (e.g. Marvel G1 Comics, Beast Wars cartoon) -- but that was because writers had relatively short notice and had to quickly wrap up complex story arcs. But a hastily made wrap up is better than no wrap-up at all, which is what happened with Energon. Had Dreamwave given Furman more advanced notice I'm sure he could have tried to bung up a quick conclusion.