I currently have 3 of them. The oldest one has been with me for 9+ years. Over those 9 years I have lost 2 fish to them --- a yellow watchman goby and a Mandarin, and both aren't the best swimmers.
I have kept BTAs with one of them, and LTAs with another one. In both cases the Haddonis seemed to stop moving around shortly after removing the other anemones. I have kept two Haddonis in the same tank without any issues.
IME, they seem very sensitive to too much flow, and prefer to have their foot buried in the sand, right at the sandbed/rock interface.
Seem to do okay under lower lights, but do better under higher lights.
I will never touch one without having a glove on, they are like Velcro. They can/will grow fast and large, depending on how often they are fed.