I just watched the first four episodes of his tv show "Important Things with Demetri Martin", and the show is absolutely hilarious. I didn't know much of his comedy before, and time and time again I thought "Mitch Hedberg could have said that"... and that is a compliment.
If you haven't seen it, I urge you to.
Ahh Demetri Martin and Mitch Hedberg, great choices! I've been watching a lot of stuff with Paul Merton recently, I'd say his style of comedy is a British relation to that of those lads. Although I don't think he was ever that great at stand up...
Please, do me a favor and don't compare Mitch to Demetri. Mitch was friend and Demetri is a shallow, harmless, girl-friendly version of Mitch. Mitch was quality, Demetri is pretty.
He's also pissed off almost every human at Comedy Central. They sent John Stewart in to talk to him two weeks ago because he was being such a cnut nobody wants to work with him. Rumor is, they won't be bringing the show back because of his behavior.
They are different in one very obvious way. Mitch Hedberg was so scared of being on a stage, that he wore sunglasses most of the time, so he could keep his eyes closed while doing his routine. It was very painful to watch him. Demetri, not so much. I prefer to listen to Mitch's shows rather than watch them.
However, I do think their humor is comparable.
Never seen a heroin addict before, huh? Mitch was nothing like that before he started using heroin.
Demetri then came along and stole Mitch's persona.
It's pretty easy to compare two people when one ripped the other off.