We have gone twice now for the Christmas time at Hershey. If you have young kids I would highly recommend it. And I would also recommend buying the combo ticket that gets you a day at Hershey and then a day at Dutch Wonderland (located in Lancaster Pa about 30 minutes south). Both parks do a great job in theme for the holidays..
Unfortunately, it really isn't geared for any children over the age of 10 at christmas as the rollercoasters are not running.
On the other hand, Hershey at Halloween is geared for everyone as all the rides are running. We just returned from there on Sunday (we returned a day early because of Hurricane Sandy) and had a blast on all the rides.