I've hesitated to add my thoughts to this discussion although I've enjoyed hearing the contributions from all perspectives.
Long and short of it is that I like my J-15 - a lot. First time I did a comparison, I liked the J-15 a lot more than either the J-29 or J-35 and thought it was up there with the J-45 I tried. Just my personal finding. Second time, I tried a different J-15 and found the same thing, so bought it. I had my heart set on a J-35 all along, so was pretty disappointed to find I preferred the J-15! I could have afforded any of those guitars but felt I had to go with the one that just felt right. I didn't try out the AJ Maple Custom the shop had in case I liked that one too much and ended up blowing my savings.
The J-15 isn't perfect - it looks and sounds beautiful but there is an issue with the saddle (which I'm replacing soon). The tuners are functional and are the same as on my Taylor 12 string. They have never given me any problems.
It suits me and the music I like to play and for the time being, I'm happy with it. If it falls to bits in the future, I'll have learned a lesson. In the meantime, I'll carry on enjoying my J-15.