There are a few videos I've seen of angels with polys, they seemed to be fine. Everyone I've talked to has said as long as the angel is a good size it should be fine.
However, a month ago I was going to buy a 4" marbled angel from a private dealer who put the angel in with a 3" delhezi, who apparantly clamped on to the angel and wouldn't leave it alone... so I bought the del. I think once again it comes down to your fish's appetite and aggression.
I really wanted angels and if he had ordered a bigger angel this could not have physically happened. If you get one grow it out or get a big one, they're both great fish.