I am not really a fan of the signature models, which I think is surprising because I was so excited about the Dave Matthews SM. Then when I saw the DMSM, heard Dave talking about it and how much the little things meant to him and what they represented, I no longer wanted one. It was too personal to Dave Matthews. In a fan sense, I would be more interested in a late 90's 914c.
I'm of the same opinion. My answer to this thread is "nobody". I think companies that build expensive, complex things need to be careful about a proliferation of models/versions. It can complicate sales and production and eat into profits, and confuse customers. With the roll out of the 2012 standard line up, it sort of looked like Taylor was trying to rationalize their offerings somewhat. While the changes to the 700 series disappointed me (and I don't mean to hijack this thread), it's ok because I went with an 800 series.
I'm sure artist endorsements do sell some guitars, but is it because someone wants to look or sound like that artist? I don't know for sure, but that's not possible. Instruments are so deeply personal, to most of us, that it is all about how one feels and sounds in YOUR hands, and you and I will no doubt pick out different guitars if we were put in a roomful of them and allowed to walk out with one each.