Really not that hard. Some people have better luck than others but if you get a healthy one you have a good chance of it doing well. The red one from ORA does really well for me.
I have two small green ones.
I think that they would not be easy.
These i have most of the times arre very good but some times they dont.
But i think that if the flower pot be more colorful(red or purple)the harder it can be kept.
Be careful sometimes some stupid sellers just color them up.
These will def die.
Goniopora stokesi is the one with the bad reputation for being difficult. The others seem to be much easier to care for.
IMHO, the key to keeping these corals healthy, especially stokesi, is plenty of food. Small particles like rotifers, or cyclop eeze.