You are going to get lots of opinions on the GSm. And most will be typical glowingly positive, if not gushy. Fine. But since you asked: I think they are good guitars and fulfill a nice little niche in the market. But frankly I do not understand what reads like uber love for these. Look at post after post, folks love them. Again, fine with me; but I just personally don't "get it." FWIW, I've seen more and more pop up in various classifeds so my guess is some folks were swept in with the novelty and/or glowing reviews ...then bought one and said "ok, it's a guitar." Just my guess, mind you. and while not slamming a good guit, I would not go out of the way to own one, personally. Now used at a good price... 
Edward
I wonder if the "uber love" comes from the fact that the guitar exceeds expectations, i.e. you expect a small travel guitar to be quite limited in tone and volume, and then you get something that's LOUD with decent tone. Even though the GS mini does NOT sound better than most ANY full-sized Taylor, it produces so much more volume and tone that expected that people get a little amped. I'll admit I've been one of those people. No, it's not my GS8 by a long shot, but to pull out and sit on the couch, where as alluded to by another poster, it's lot easier to handle makes it a nice addition. Not to mention the shorter scale is making me create in a whole new way...you venture up the neck more when it's not such a far distance away! Also, people who generally can't afford a full-sized Taylor can get a little closer than before with the mini, as it definitely is an improvement over the baby and big baby, at least IMO.
There are negatives: 1) the es-go sounds a little tinny and cheap, 2) if you use it live, it'll be a big drop off from your main Taylor, and 3) it's a laminate, etc. but overall, you feel you're getting a lot more guitar than its small package belies.
This, IMHO, explains the craze over the GS Mini.