From playing Merion East on consecutive days, after being on site for the Walker Cup (photos) and years before the Curtis Cup (photos): I learned that Merion East demands great execution on each shot, and suggests that you look for the best places to aim and land your ball. I also learned that the manner in which the world's top amateurs tour a course, bears little resemblance nor symmetry to the manner in which we the common, tour a course.
From playing Bethpage Black: I learned that a public-access course can be maintained in a private-club manner, if the municipality cares to do so. I learned that extraordinary length may be required to play holes in the manner espoused by the caretakers, and that I am in short supply of said length. As a result, I must use my guile and wisdom, but I must also understand that I will not be in possesion of both on each and every shot.
From walking and photographing Crystal Downs, while my three buddies played with our host: I learned that I desperately wanted to play Crystal Downs! I also learned that I wanted my one generous buddy, who offered to let me play the back nine in his place, should play the entire 18, to have the complete experience. I don't know that I'll get back that way again, but I did enjoy walking the course and finding the best angles for photography.
From playing and shooting Pasatiempo: I learned that any MacKenzie course is a treat, especially those that are valued as MacKenzie courses (courgh, Scarlet, cough.) AM was a rare breed among all the rare, great architects. In fact, he may not have been a breed at all, despite the hackneyed saying. I learned that long and deceitful holes go hand in hand with short, deceitful holes. I also learned that the 18th at Pasa has a twin across the country, in the 18th hole at Zanesville Country Club.
From playing courses at Bandon and Sandon (Sand Valley): I learned that width is a huge balance point for extreme movement. The land can heave and ho all it wants, but if you give a golfer room, event the sloppiest strikers will have a chance to make the next shot.
From playing NGLA: I learned that some golf courses inspire you to play better than you thought you could. I had seen NGLA at the Walker Cup (three days of photos) and when I had the chance to play there, I could not believe how well I played holes 4 through 18 (the first three were a gentle warm-up, shall we say.)
In conclusion, the element of great golf courses that separates them even more than the routing, is the putting surfaces. The blend of speed, undulation, and tilt reduces us all to naked competitors. We have no place to hide.