I did the Pershing Square one last month and it was a blast! Not all of the food was particularly interesting on that tour, but the tour guide was adorable and personable and we had a great time meeting the other members of the tour group and walking around downtown. I thought it was also a great value (especially since we bought our tickets off Goldstar at a discount) for the amount of food we had a chance to sample. At the end of the tour, I discovered there was a fellow hound on the tour and it's always incredibly exciting to put a face to a chowhound handle :). I would highly recommend.
I think it looks like a lot of fun. I've probably been to many of the places they feature, but it would be a great way to get an introduction to some of LA's best ethnic food neighborhoods. Would love to hear if anybody has had a good experience.
I'll volunteer to lead a Vietnamese food tour.