I usually send my feedback through email but I've gone to City Hall, too. I've also tried to give way more compliments than complaints.
Some of the compliments:
1. The Halloween party (overall) in 2012
2. The CM playing Merida at the Brave M&G - we thought she was excellent
3. A CM at the Haunted Mansion who let us go see the original pet cemetery (we didn't mention this specifically in the compliment; we said he went out of his way to help us, etc. because we didn't know if mentioning the cemetery would be a good idea)
4. A CM who noticed us looking at the old Skyway station, took a photo of us standing in front of it and tipped us off to the best place to get a good view (the Casey Jr train!).
5. Maleficent at the Halloween party!
I've only made a handful of complaints:
1. The truly rude CMs at the 2011 Halloween party (who included a CM who was muttering under their breath, a CM who was shouting and ranting at the people waiting for the tram, CMs who completely ignored guests for their personal conversations, etc.). We didn't give names; we just gave examples.
2. The Matterhorn bobsleds.
3. A situation at the Matterhorn with a CM. I didn't report this at first but after thinking it over, I did.