I like Bumblebee having a face, and most importantly a VOICE. In Prime Bumblebee was mostly just sorta there, though had a few cool moments. I also really do like him being the team leader, but the writers haven't really let him fully take on that role yet. It seems like when Optimus steps in he's the one to ultimately save the day.
Jazz's inclusion is forgettable. He showed up to sell a figure(pretty early on) and that's it. No mention of him since, and it doesn't look like he'll be coming back.
The humans aren't bad and rarely eat up screen time. The Season 3 opener is a good example: They had a story but it didn't take any more time than it needed to.
Steeljaw as a "main villain" was very underwhelming to me. There wasn't anything really unique about his character or voice. His rogue team of cons was a nice idea but I can't remember them doing too much original.
The Season 2 "overlords" of Saberhorn and Glowstrike barely register. I have to use the wiki just to remember their names. Looking at Glowstrike's page...huh she
did transform.
Ratchet's small part in Season 2 was welcome(though his mini-con wasn't super effective) and Soundwave's return was a very nice bit of continuity, and one of the best episodes. Which brings me to my next point: where are the Prime kids? They'd be a bit older now yes but would be a very much appreciated addition to the story, even as a cameo
Season 2 1/2 was pretty good, and Steve Blum's Starscream is always a treat. I liked how the story flowed and even the mini-cons were given some characterization.
Season 3's start isn't too bad. Hopefully the Stunticons stick around for more than just a few episodes.
Finally, if there's one Decepticon I want to get a figure more than anyone(though I know he won't) it's....Malodor
. He's a silly character, but the idea of a Skunkicon is amusing to me and it reminds me of one of favorite MOTU characters, Stinkor!