My last comment was brief because I was in the middle of work (I've only just gotten home) and didn't have time to elaborate on my views - but what you guys said about IDW writers expanding on the source material is correct.

Anyway, in the intended spirit of this thread, here are my favourite new characterisations of G1 characters. I've got 2 categories:
* Favourite expanded characterisation - this is where the writers have taken the original character's G1 persona and built on it.
* Favourite new characterisation - this is where the writers have basically ignored the original character's G1 persona and made something new.

Favourite Expanded Characterisation: Ironfist
In the toy's original bio, we know that Ironfist is a genius and crafting all manner of weaponry. Kinda like the Autobot equivalent of Hephaestos/Vulcan or Howard Stark. He forged new weapons for the Autobots. But that was more or less all we knew. The IDW comics delved way deeper and also gave him the additional personality trait of being this nerdy engineer -- cooped up and an extreme fan-boy of the Autobots in the field, especially the Wreckers. And of course the fan admin of Autopedia.

Other honourable mentions: Swerve, Hubcap, Thundercracker, Whirl

Favourite New Characterisation: Tailgate
IDW is nothing like his G1 persona but still an extremely cool character!

Other honourable mentions: Cyclonus, Star Sabre, Pyro, Rotorstorm