I've been to the one in San Diego and Chicago, and they have a great atmosphere. If it's anything like the one in SD/Chicago, then it's a great place to catch a local band play, or even a big name band. It's cool when bigger names roll into town, and you catch them in the relatively smaller venue with a smaller crowd (obviously, you have to buy tickets waaay in advance for that). I like it how they separate the 21 and over, under 21's. I've never tried their food though.
The venue size of those HoB's were pretty small. About small to medium. I guess they were more meant for local bands to just jam to anyone who wants to come in to listen to some good stuff. I don't think anymore than ~300 can even fit in any HoB... I went to a Lily Allen + Bird and the Bee concert, and there were roughly ~200ish, and I felt that was pretty packed.
As far as venues go, I particularly liked "The Grove," which is near where the Angel's Stadium and the amtrak station is.