John:
I feel that if you walk a course and you are really paying close attention, you can learn more about it than you will from following around your own ball in a single round. But, ideally, you would do BOTH, so you had a feel for the shots but not just the shots you happened to face.
I don't know that it's so easy to judge a course if you just see it from outside the ropes in a tournament setting, though. I've had more trouble getting a feel for the course if I can't stand on the spot from which the player is going to hit his approach shots, and also if I can't walk on the greens and get a good feel for them. I suppose if you watch a bunch of players putt each green, you can get a sense, but that's not as quick as doing it yourself.
It's funny, too, that most raters who play courses either (a) play alone, or (b) play with other raters. I can't imagine a restaurant critic taking either approach. A restaurant critic would want to dine with several other people to see a wider selection of entrees, but he wouldn't want to dine with a bunch of other critics who were expressing their own biases.