It's brilliant. I go every year, without fail, and never regret it. Just be sure to take plenty of money with you as it can get a tad expensive. Still, totally worth the money spent. Plenty of entertainment and it's not all outdoors like people assume, it's sheltered in cute wooden huts and the food - aw, man, the food.
Seconded, never fail to visit(multiple times!) The only problem is that on a weekend it can get implausibly busy. So much so you can actually get stuck in there and lose all hope of ever leaving Germany! If you can go earlier in the day/early evening it's great though. My recommendation for food. Knobi Satt: The most potent and awesome garlic bread ever. Also, don't forget to tip your hat to the singing moose.
P.S Hello BritGAF, first time application post.