Energon wasn't a bad series IMO, but wasn't a great series either.
The Autobots were pretty awful all over as they were mutilated by the combining thingo. Pants or torso? Dunno, they both looked pretty pants to me. Fattimus was just horrible. Poor small mode and ridiculous super mode. I do laugh at his himer simpson-esque 5 o'clock shadow (as I see it) on his face. I can't believe that that thing cost me $100 too! It also gave us our first general release Arcee as well iirc.

The Decepticons were pretty good though I think. I particularly liked Mirage, but was a bit annoyed by who they were nerfed majorly by the insistence of putting sound chips in them. I was also excited to see that they release a fair few USA characters, Slugslinger, Towline and Sharkticon were pretty good little figures I thought and didn't get released in Japan until much later. Some not at all I think.

I didn't really bother with the ~maximus teams much as they looked half arsed to me. I did like it as they released Microman kicker, my first Human Transformers character in my collection and started me on Microman figures.

I think My first one was Starscream. I got a few Super link figures and Stars was an SL.

My favourite would have to be Demolishor, cool robot and dumptruck dude with a HUGE rack (of missiles).
Honourable mentions for: Rodimus, who doesn't love a souped up racing truck thing? Followed closely by Mirage.

Worst would be, Um, Fattimus Prime, without a doubt. Ugly, stupid combiner mode and expensive. I remember buying it and after opening it thinking:
"I paid $100 for Power Pants and he has an awesome trailer packed full of self transforming sexiness. I paid $100 for fattimus and I get a Box to hold some crappy vehicles that looks stupid..."

I am not really looking for anymore. I have my Omni/Terror?Horror? cons? And the characters I liked. So I am satisfied.