I have one... from my experience, they are not extremely fragile (certainly not hardy either), they are just very moody. This can be a problem if you have more than one because they are very sensitive to other corals near them. If the flowerpot becomes unhappy, it has the ability to release a toxin into the water in attempt to kill nearby corals. From what I have heard/read, the toxin from a single flowerpot is not deadly to most stock (only the most fragile/sensitive), but the toxin from multiple flowerpots can wipe out a reef.
With all that said, my flowerpot has not been happy in a couple of weeks, and I think it is a lighting issue. I run standard lighting, and I had to replace the bulbs about a month ago. Since then the flowerpot only comes out first thing in the morning, and late at night (when only the actinic bulb is on). If you can find a place where it is happy, DON'T MOVE IT. It's tough to make flowerpots comfortable.
Good luck with him... they can be frustrating, but I think it's worth it if you can get a happy one.
Oh, btw... be sure that you don't touch the stony base of the coral with your hands/fingers. The oils and junk on you skin will kill animal where you touched it. I find it's best to use one of the plastic bags that my LFS sends stock home in like a glove.
[ July 24, 2001: Message edited by: jacksonpt ]