Bought a '13 Explorer a couple of weeks ago and so far I've found a lot to like and very little to complain about. My real use for this bike is as a sport touring machine with a few excursions down forest service roads and mountain logging roads. I have no plans to take this beast into serious technical off-road situations - I have a 300 lb. dirt bike for that shit. On fire roads and such I don't think most of us could tell the difference between the Explorer and a BMW GS. But on the road this bike nails it when compaired to the GS, much more fun through the tight stuff. I think a lot of adventure touring bike owners use their bikes mostly on-road and their off-road excursions are generally pretty tame, so for a lot of us this bike makes sense. For the few who ride any of these battleships in a serious off-road environment then, from what I'm told, the GS is still the bike for you - I, personally have no desire to, or the skills to take a 500+ lb, $18,000 bike on anything but fire/forest service roads. When I'm traveling this bike will allow me to explore roads I would not do on my previous sport-touring mount ('10 Kaw Concourse) but still have a blast on the great pavement in NC, TN, WV, VA etc.
This is one of the most comfortable bikes I've ever owned and I the motor is fantastic, the only complaints I have are engine heat on the legs in hot weather (only noticeable if only wearing jeans without overpants) and wind noise from the shield (I've bought another stock shield and plan to cut it down, that may eliminate some of the noise)
So, all-in-all I think it's a fantastic bike that should be on anyones short list if you are looking for this class of motorcycle.
Triumph Tiger Explorer
Triumph Speed Triple
BMW R-100 S
Triumph Tiger 800 & Ural Patrol-T (wife's)