Martin now makes so many similar models that the choice is really difficult. In addition to the 000-15S, they make a 000-15 (14 frets to the body, an OM-15 (same as the 000-15 except the scale is slightly longer) and a J-15 (a king sized 0000-15)!

000-15S owners, how easy is string changing?

All the best,
Dan Milner