Personally we've stayed clear of Active DCS. In the older 9.x track, about 2 years ago, we had a lot of issues with AP's rebooting due to DCS being in active mode. Recently on the 10.x release, DCS wasn't reporting correct threshold numbers, which was fixed in 10.11.05.
I would love for DCS and auto tx to work flawlessly, as micro managing channels consumes more time than I would like. Now that the firmware we are on seems stable, it might be time for me to re-visit DCS functionality.
I've also run into the same thing where Auto channel selection chooses the same channel across AP's, but i never knew that manually running ACS was recommended after boot. That's really good to know and i'll have to play with it at some point.
I'm also interested to hear from anyone who is successfully using Active DCS and what thresholds they are using, specifically in a dense urban environment.