Bandon Dunes planted a mix of fescue and colonial bentgrass.
At Pacific Dunes we recommended keeping the colonial bent out of the mix, but in the end we went with what had been successful there [up to that point].
Bandon Trails did the same, but with less colonial bent.
Old Macdonald's greens were planted with pure fescue to start.
The first three courses have mostly gone over to Poa annua now. Old Mac was still mostly fescue the last time I played it, 18 months ago, but it is not as old, and I wouldn't bet on them holding off the Poa another 5-10 years. Sounds like they are starting to lose that battle, from your description.
Even so, Ken Nice feels that fighting off the poa annua for as long as they can is a good fight. Some poa annua plants are much more drought tolerant than others, so the longer you fight the good fight, the more drought tolerant the poa you wind up with.
Honestly, I don't care so much what grass is on the greens -- I care if the surface is firm and if they are running true. But I also care if the conditions on the aprons are markedly different than the greens, and that's where having poa or bent, at a higher height of cut, is a clear step backwards from having fescue all the way through. When the courses opened I could putt from 40-50 yards off the green, without making a significant adjustment for the speed of the apron vs. the speed of the green.