I flew in Trenton, NJ for my Multi-Engine Commercial add-on. My instructor was Matt --- he isn't there anymore because he is at XJT.
My overall experience was fantastic! The staff was very friendly, and very helpful. My DPE was also a great guy, and we are friends to this day.
My only beef with it, is that I was trained to pass the checkride...and that's it. You have to do all of your "book learning" on your own. (now if you are going through the whole "pro pilot" course, it may be different?) Fortunately I had a Multi-Engine ground school in college, as well as preveous ground training with my instructor back home.
Over any of the other academys, I would definately endorse ATP. Good luck in whatever you decide to do.
Lax