It's more of a "feel" issue for me. If I don't need the 7th, its nice not to have it in the way. I'm planning on buying a JP6 next year. Having one of each will be nice.
As far as the neck goes I don't notice, and I switch from six to seven and I also play several diffeent neck profiles in the seven string category. As far as the concept goes, I don't even think of it as a seven string, I play it just as I would my six, in fact I will write a tune on my six and then play it on my seven, same position, different string...(obviously in a lower key)