Muirfield is one of the three best courses I have played, the others are CPC and Dornoch. If forced to choose one of the three, which I find impossible, it would likely be the winner.
It may lack quirk (though even that is a little unfair, there's a wall in play on the 6th and on the 9th, a blind tee shot on 11 and semi-blind approaches on 8 and 9) but it is excellent golfing ground (not as roly-poly as St Andrews but there's plenty of contour to consider), it has a famously excellent routing and some of the best bunkering around (perhaps the excellence of the bunkering distracts some critics from the other features of the course). Unlike Brent, I think the absolute stars of the show are the par 5s. Certainly the strongest set of par 5s I have played. It doesn't have a driveable par 4 but 2, 3, 11, 12 and 15 can all, in the right wind be drive and pitch holes and each an excellent example of the genre. The longer par 4s (1, 6, 8, 10, 14 and 18) are a seriously tough proposition but, again, are all excellent holes.
It's reputation as a tough course is fair but it remains playable by all. Even in a warm, wet summer like this you have to be pretty wild to lose a lot of balls. I was there a couple of weeks ago and lost one ball in the day and that as a result of a shank from a fairway bunker on the 1st hole of the day and I am a very average player.