Hi,
I was just there this past Saturday and have a few recommendations/comments for you.
First off, you will NOT have enough time to do all SIX haunted houses/attractions that they have. The lines for the haunts are very long (after all, they are free with admission). I was able to do all six, however, because the park allowed everyone who attended the coaster event this past Saturday front of the line access to all the haunts. Since you will only be able to hit a few, here are the ones not to miss.
#1: Circus of Horrors in 3D. Everyone in my group ranked this as either the #1 or #2 haunt at the park this year. Though not extremely scary, it had a few startling moments. Best of all, the 3d effects were quite awesome. If you do this one, don't rush through it. Make sure to go slow and check out all the sights in 3D.
#2 Massacre Manor & #3: The Asylum. Both were pretty good. Everyone ranked these in the top 3. If my memory serves me correctly, the Asylum is the longer of the two and features TONS of strobe lighting. The Manor is a bit shorter and also features less strobes.
The worst ones are Headless Hallow (train) and Cowboy Carnage. Psycho Path (by Flight of Fear) is probably the best of these 3, but it's not as good as the top three I gave you.
Also, in general, the park will start out very fast in the day, and just get busier and busier all day long. The lines for the haunted attractions will be EXTREMELY long, so consider lining up for one before it starts.
Overall, the haunts are pretty good, and the park is somewhat decorated for Halloween. The park does a pretty good job of spreading fog throughout the park (there sure was a heck of it still visible during our 1am Beast rides). They don't have as many characters walking around the park as say, Great America, but what they might lack in that category they more than make up for w/ all the free (with park admission) haunted attractions.
One other tip...skip the magician. I thought it was a very lame show.
So, remember, if you want to ride anything, get there at park open, move as quickly as possible from ride to ride, then prepare to wait...for quite awhile ...for all the rides and haunts.
Have a fun trip!!!