Some are considered hard but if you have the right conditions they shouldn,t be that much more difficult than a NOID phal .
Phal gigantea is supposed to be slow growing & prone to crown rot.
Phal bellina semd to grow like a weed if it,s kept slighlty moist all the time.
Most species will grow under the same conditions as the more usual hybrids with a little tweaking of conditions(a little more light , heat).
There are some species that require a cool but bright winter , this may be difficult to achieve for a lot of people.
Getting them to flower is a whole new ball game though.
Just have to look up the particular 1,s your interested in & get some info of the WWW.