The food is good, the atmosphere is fun, the beer is BIG (the way it should be). Be warned that you will in all likely hood be seated with another party or two. This has never been an issue for us, however, depending on who you sit with can make or break your dining experience. On our last visit, my girlfriend and I were sat with a couple who was a little older than us, and a family of 4. We had a blast with the older couple, drinking, laughing, talking, having a good time, while the family of 4 didn't say a word to us or eachother the whole meal. If we sat with only that family there is no way our meal would have been as enjoyable as it was. This is not to scare you from going to Biergarten, it happens to be one of our favs., it is just a little heads up.
Enjoy and have fan!