Well the "with caution" bit is often given with all pygmy angels, it basically translates to "they may or may not" be reef safe... I know it's ambiguous as all hell but the fish's personality comes into play with them. I had one that didn't touch a single coral in my tank(that I saw), then I got an open brain (cats eye) and a freebe which was on it's last legs (LFS owner just wanted it out of the house) well the one I paid for apparently was tasty as it picked at it until it was dead (which took surprisingly little time), the one that was dying, has come back with a vengance and now is quite a pretty piece in my tank never touched by anything.
So its really a coin toss, if you have any particular corals that you consider "prize pieces" I wouldn't risk it, if you don't have anything in particular then go for it, it most probably won't decimate your entire coral population. Look to some tanks of the month on this (and other) sites quite a few have large angelfish (Imperators) which are most definately not classified as reef safe but some have them. Its all a matter of if the fish has a "sweet tooth" for a particular coral
I have gone through 4 angels in the 125 I built. Started with a Coral Beauty and a Fishers Angel. Then I added a Bicolor. Fishers dissapeared, and Bicolor had some disease. The Bicolor got better then up and died. Then I picked up a Half Black and it has also dissapeared. Now the Coral Beauty is the only one left.
Of all of them, I did not see aggression among themselves.
Anyways, to the question. Only the Bicolor picked at corals, particulataly a favia and nothing else. I took the favia out and placed it in another tank and now it is doing much better. None of the other angels seem to bother the corals.
Our coral beauty behaves itself quite well and hasn't touched any of the corals in our tank - a mushroom, bubble, open brain, birdsnest. Just added a corcea clam a few days ago, so far so good. Our blue zenia perished, but I never did see the coral beauty picking at it - I think snails were the culprit. I think like I have read many times on this site - each fish has its own personality and it is hit or miss. Ours is probably the favorite of the fish in our tank - it is a great swimmer and is fun to watch darting in and out of any hole and passage it can.