We did the evening hours at EPCOT and MK last week. At EPCOT the line for test track was still over an hour, but they did have the fast pass machines still running, so we did that. Mission Space was a walk on (but then again, it was a walk on all day). Everything else that was open seemed to be a very short wait. Saw HISTA with about 20 other people in the theater at 11PM.
MK was crowded early, but thinned out. Walked onto Splash and BTMRR right after the fireworks, but then a line started to build. Waited 15 minutes for the Magic Carpets (don't ask me why). Went through Fantasyland after 11PM and there was NO ONE there -- if you have little ones that can make it til midnight (my 5 year could do it with an afternoon nap), that would be the time to do Fantasyland! Some of the rides, like Jungle Cruise and Splash, are so much better at night!