His show is hit or miss, whoch shouldn't surprise anyone. Whenever a stand up comedian gets a show, it is NEVER as funny as their stand up, because they've always had more experience in the stand up world.
This is true even for Chapelle's Show, which was pretty damn funny. Even though his show was funny, his standup was easily funnier and more consistent. The reason his show was god was probably because Dave had experience on TV and in movies as well as stand up comedy prior to having his own show. Demitri Martin really only knew stand up and brief stints on TV, like on the Daily Show for 5 minute segments before he suddenly had his own half hour slot.
Trust me, Demetri Martin is funnier in a stand up setting where he has complete control.