Definitely agree on Oakmont.
Ill throw out 2 more that have not been mentioned yet.
Grosse Isle CC
Royal Cinque Ports GC
Zowie - never thought I would see Grosse Ile pop up. In many ways the greens are mini versions of Oakland Hills, but I think as a set they are more varied than OH. Still, I am gonna go with Oakland Hills because I think the greens get more interesting due to the shots required into them. I have never seen a better set anywhere. They could only get better if the course was widened out a bit. Some of the crazy angles would really shine.
In terms of conditioning, and without any shadow of a doubt, at least in the past many, many years, Nairn. I couldn't believe how perfectly prepared in terms of balancing speed and firmness they were.
Most recently in the States, the best conditioned greens I have seen were UofM's. In fact, for the combination of conditioning and interest, UofM's greens rate pretty damn high.
I suspect Old Town's would be superb as well. Unfortunately, I didn't catch the course in its best shape.
As for England, I think the best set I have seen are Beau Desert's - superb variety. Unfortunately, they are rarely in the condition which makes them a terror. That said, both Huntercombe's and Woking's are cunning sets.
Conditioning seems to be a problem up and down the country these days. I recall greens in general being in much better condition 10-15 years ago.
Ciao