Never broken a cup. I used the AP with paper coffee cups, styrofoam coffee cups, glass, Bodum double wall cups, ceramic, etc. and never had a problem. IMHO if you are pushing down hard enough to break a cup you need to adjust your grind. It shouldn't take all that much pressure to press the plunger. In the past I've used grinds that took so much force it probably would have broken some of the more delicate cups, but I've found that a slightly coarser grind works better and requires less force.
I have almost tipped a cup a couple of times, but I've never been past the point of no return.
I think I still rate the AP as probably the best
all around brewer in my arsenal for several reasons:
First and foremost it produces a fantastic cup of coffee.
It's very forgiving with the grinder and grind being used.
Lightweight
Ultra-portable
Works with lower water temps.
Cleanup? Fugetaboutit.
Inexpensive
Versatile: makes lattes, americanos, & expresso (see video below for clarification)
Okay, I'll admit it's not the prettiest device in my arsenal, but still a pretty impressive resume if you ask me. Sometimes my AP sits used for long periods of time, but I always end up going back to it and it ends up impressing me all over again.