I have heard that they are easy given that they get rather strong light and high temperature.
Then again, when people say that certain plants are easy or tough, they have to say why and what kind of conditions they are growing them. Otherwise, it's all useless and add to the confusion and frustration I guess.
I have a hybrid of niveum (I have four of them), which is a cross between Greyii (angthong var. alba x niveum) and niveum.
I can really see why they are warm grower. They did not do anything for the entire fall into spring and my place stays fairly warm.
Now that the weather is getting really warm ( well, it is cool now again in NYC but we did have some crazy summer like weather earlier as well, right?)
all four of them are growing like crazy!
Mine get strong sun on and off throughout the day along with my leucochilum.
hope this gives you a little bit of hope.
Just get one ore four, and find out!