A rhino would be perfect for a reef, as they have no interest in corals, nor do they perch on them, as their lionfish cousins occasionally do.
As for "hard to feed", I can't say that I agree with that, altho we did have one specimen that wouldn't QUITE get "on the stick", which was a PITA. FWIW, we've kept four Rhinos in the past...
R. frondosa (x3) and
R. eschmeyeri. I strongly recommend using a "stealth stick" as described in
Tools of the Trade: Equipment & Techniques to Convert your Fish onto Frozen
Rhinos are very sedentary, and don't swim much at all, if ever. They do require some open space on the substrate, and will get up onto the rockwork if there isn't enuff space for them. The nice thing is they're very out and about fishes, so you'll always see them in your tank.
Being sedentary, and often looking like macro algae or rocks, they're prone to being picked at by browsing species (tangs, rabbitfishes, non-planktonic feeding triggers, angels, puffers, etc), so if you keep any of these, or plan to, a Rhino isn't a good fit.
If you have any more questions, ask away...