One additional point...
>>> Still, I've sure been hesitant to ask for priority handling with a real problem onboard if it looks like we're getting in with no delay. If delays are announced, it does put me in a somewhat suspicious situation if I then request priority, as you point out.
Just to clarify, if any a/c actually declares a PAN (or MAYDAY), be it just after the delay has been announced or 2 miles short of the hold, or indeed when you're the only a/c on frequency, no controller would question your judgement. As far as we're concerned if you declared either we'll offer every possible assistance and the seas will part - no question