I think I have been fortunate enough to play 40 or so rounds of golf at Oakmont over the years; the majority of those in the late '90s and early "00s (?) and only two or three times since the tree removal was started/completed.
If memory serves, and without any sort of agronomy background at all or even a green thumb, I can recall only two greens ever having unique problems/issues that stood out from the set. Yes, although it may be heresy, there have been brief periods in time when I have played there, or heard from a few of my member friends, when the overall condition of the putting surfaces were in less than their usual, stellar best.
I seem to remember a fan behind the first green at some point. I'm not sure any tree removal program would give that green complex adequate coverage or air circulation based upon where it sits on the corner of that side of the property.
The other green that I can remember having issues is the 8th. There used to be a line of pine trees, scotch pines I believe if those are the type that have the foliage beginning at ground level (remember I'm from South Florida). Several greens had this sort of wall of trees behind it, 16th for one. But while the pines behind the 16th were at least 15 or 20 yards down at the bottom of a significant slope, there wasn't much more than a few yards between the back collar and the pines on eight. I haven't the foggiest (did I just work the word "foggiest" into a post [?]) what the compass position of the green with relation to the trees and the angle of the sun but I do remember rather frequent and recurring problems with the condition of that green, especially on the back third of a fairly large green. I do not recall any other trees close enough to have an effect but if there were there ain't no way they are anything more but mulch now.
Again, this is off the top of my head and please forgive the layman's terms.
For those of you who have more significant and/or recent experience at Oakmont, or are lucky enough to play there on a regular basis, does any of this ring a bell (and is that fan still behind the first green or any other green)?
Finally, though I'm born and raised on Bermuda, I have played a fair amount of golf on bent grass greens, especially in the Northeast. But I have never seen any putting surfaces anywhere else in the world that look quite like the greens at Oakmont, forget about the fact that they are slicker than snot on a doorknob. They just look unique to the untrained eye. Can anyone else comment or explain this to a guy who has played a lot of golf but admittedly can't keep a silk house plant alive?