I'm a big fan of Muirfield and would categorise it as one of those courses where the whole is more than the sum of the parts. I agree there aren't any weak holes, though it is also true to say that there are probably not that many which are really memorable. Overall I would agree with all Mark says about the course, including the bunkering. If you are as modest in the sand as I am, you do not want to visit some of these places. The coffin cross-bunker on the right of the 17th is not a place you want to visit in a medal round!
If I had a criticism it would be that I still struggle in my mind to separate 12,14 and 15, despite having played the course a number of times. More fool me! I agree with James that it is a course whose appeal unfolds over time.
My favourite holes are 2, 3, 6,8,11, 13 and 17 - probably the holes with the most character, and possibly challenge too.
Two reasons why it is such a good experience over and above the merits of individual holes are: first, it is a fantastic property/routing, and the ability to see so much of from the clubhouse is a very attractive feature. Second, the clubhouse evokes the history of the game more powerfully than any other i have visited. And, whatever its foibles, it is obviously a wonderful club - I always love visiting it. There are not many golf experiences that can equal a visit to Muirfield.