At the time of writing, the site only lists one entry for commentary, but there are multiple tracks on the set. This is a review of the first one, on the first episode, which is show creator Bill Lawrence, Zach Braff (JD) and Don Faison (Turk).

This is a terrible track. It's basically the three of them laughing at the show. Zach asks a question about the Phen Fen (or however you spell it) gag, and how it got past legal, and his question is ignored.

Don't waste your time on this after the opening credits. The only interesting facts are all before they roll. (I won't spoil them for you.) A fantastic show, and a bloody awful commentary track.