Just a very quick review to back up (in part) the remarks made by the last 2 star reviewer.
Some of the music is a little puerile as already mentioned - Titties and Beer - but then again that's Frank Zappa, and I suspect some people (many) enjoyed these little stage shows which musically probably lead nowhere, especially when you're just listening and not at the concert itself. However, these humorous moments were linked in in a better way as can be heard on 'Live at the Roxy and Elsewhere'.
After saying that I would say that the second CD in this collection has some excellent music, and less comedy routines, and so is more what you're expecting from Zappa, in fact I just bought this as I couldn't find (in my local store) a copy of 'One Size Fits All' which by all accounts is really the one to hear. But, saying all of that if you enjoy Zappa live (some long guitar solos), and great version of 'Sofa' with the Brecker Bros providing the horn section, a stunning version(s) of 'Black Page' (1 & 2) and several other great tracks then you'll enjoy this.
Zappa live (on record/CD) probably let his hair down a little more than in the studio, so obviously what you get is slightly longer guitar solos, blah-blah, and general fun. I agree that the Roxy album is tighter, stronger, and the sound/mix* is better, but if you can find this at a good price then it's certainly worth buying.
If you're a Zappa fan you probably bought this when it was first reissued due to the extra tracks - i.e. the original album was restored by Zappa when he got his contract back, meaning it has more material than the original vinyl edition.
*= the way this has been mixed is VERY live, almost as if you're in the public. However the room where they played seems to be very bright and resonant. They (he) seemed to want this effect, whereas on the 'Live at the Roxy' the sound is very direct - i.e. you don't hear the public so much ...... which makes it clearer, more direct and of course more detail. But, one has to assume this is the way FZ wanted it.