I have two Martins, a 1968 D18 and a 2000 SPD15. I've owned the first for over thirty years, sold it to a friend twice when broke and bought it back again when solvent. It's like my wife in a way, I love it dearly, the years have mellowed it more than somewhat and I don't take it out much any more.
The SPD15 was a love at first pick indulgence for which I traded in a Simon and Patrick (pretty good, but FRAGILE finish) and a Washburn J200 copy (big, powerful but I prefer the sound of a Dreadnought).
In my time I've owned several guitars (I used to teach guitar and trade), and still have three Washburns and a 1978 Mugen, but I always come back to the Martins.
I don't play bluegrass, but I was (and am) heavily influenced by Tom Paxton - even if he doesn't play Martins on stage these days.