I don't understand what you're getting at when you mention the fact that Universal has a lot of ex-Imagineers. IOA opened, making UO a full-fledged resort, a whole 2 years before DisneySea did.
Best "haunted" ride - The Haunted Mansion, of course.
Best walkthrough - Scream House from HHN12. They recently posted the creepy-as-hell queue video for this classic at HHNVault.com.
It's been pretty long since I've been able to go to IOA during nighttime hours. The last time I was there at night was HHN, but that's not the same. That's a whole 'nother atmosphere altogether, equally photogenic though.