I "discovered" bamboo about 6 years ago. Mostly as I was delving more into the history of fly fishing. First of all no fly rod is as beautiful. I do like the slower, softer action of bamboo over graphite and as others have said, when you have a fish on there is no comparison to bamboo. It's also in what you like.
A big factor for me is that I simply enjoy doing things the "old way". Muzzleloaders, long bows and bamboo fly rods. The last couple years I've been visiting old style wet flys but fishing drys is still the most fun for me.
Vic