My honest thoughts:
The theme is very well executed in Haunted House. The sounds are good (in my opinion) and the organ music is OUTSTANDING.
I used to have one, and sold it LONG ago. It was fun for a while, but (as with most widebody machines I have played) I found it to get boring very quickly. This may be more a result of me not liking widebody machines more than Haunted House being a boring machine.
The kick targets are cool, the art is good. The 3 level playfield is novel. I really like the light sequencers int he backglass to give the lightning effect.
They can be problematic to keep running, but there are many upgrades that can amke them MUCH more reliable.
Also, it is the single heaviest pinball machine I have ever moved. Built like a tank.
The prices I have seen lately are $900-$1600 depending on condition, upgrades, etc.
Good luck. Many really like this machine. Personally, I wouldn't care if I never played one again. But then again, I really like Spectrum, LOL.
Chris