We went to Howl-o-ween and it was very hard to get in. Poorly organized at entrance. First you wait for 45 minutes in 1 line to buy tickets (which my daughter had lost). Then you wait in another line for 30 minutes to get into the zoo.
The event itself was fun, beautiful light exhibition. I think the zoo should offer it on more then 2 nights so that so many people aren't trying to get in.