When I ran heights in my set up the effect was subtle. However when I turned them off it was noticeable that they were missing, my front sound stage collapsed for lack of a better word...not that it was bad without them just not as "big" sounding. When they were on I mostly couldn't tell that they were on, and I often times had to double and triple check that they were indeed active.
I've read posts on these forums stating that the heights are only good for sound effects that should be coming from above you, and while it did add to certain scenes with overhead sound, they also created a large sound stage and music scores, sound effects overall were both enhanced by the heights...not just overhead directional effects. But if I didnt tell you they were on you probably wouldnt guess that they were on until I turned them off.
You can try out action/sci-fi blu-rays. Transformers and Star Trek 2009 both come to mind.
I don't need snobs to tell me how to think, thank you!