I've been to the Isthmus Beer and Cheese Fest at least 3 years running now, and it never fails to disappoint!
I highly recommend springing for the VIP tickets which allow you to enter early before the rest of the crowd. We did that this year and it was nice spending time there with no lines whatsoever.
Every year they feature a great selection of craft beer and of course cheese. I think each year the cheese/snack selection improves. When you enter you are given a glass (which you get to keep) and from there you can just walk up to all the booths to sample the beers.
There are plenty of vendors serving, and so while you may find some short lines, they all move quickly.
There are usually some fun activities/live music and other types of entertainment.