What were your thoughts aside from a heavier bike w/ a bigger gas tank? Ride, handling, reliability, etc improved,
Starting with the 2008 model, I've done at least one fairly good trip (>3,000 miles) and often two on most all the model-years since then.
Heavier? Are they? I wouldn't say that the 2015 model feels any heavier than that first 2008.
Those first years bikes hardly even seemed waterproof. Pretty much all the ones I rode had problems after a heavy rain--ranging from total ignition failure to a failure of the dash to display anything to just the annoyance of a foggy display. The later ones have been much better on that score.
The early Stelvios weren't too good at slow speeds, sometimes feeling like they had a sloppy final drive chain. That's now much better (feels like a driveshaft, again).
The early Stelvios sounded ghastly while idling, The newer ones are much better, although they're still pretty rattily. Ear plugs are the answer, here.
That small tank (and the goofy cable actuated glove-box lid it came with) would have been a deal-breaker for me. If I had to choose between buying a small-tank Stelvio and a Griso, I'd take a Griso.
This issue has been the same, forever: The short Italy side-stand is worse than the longer U.S. side-stand (I'm not sure which countries get which stand).
So has this: The Italy mirrors are much better than the U.S. mirrors.
Seat height adjustment is now easier than what the first bikes had.
All of them. Fuses: Why does Guzzi scatter the fuses here and there? I look at a Triumph with easy-to-find and well labeled fuses and can only sigh with admiration.
Overall, from 2008 to 2015 every Stelvio is really much more the same that different. I'd prefer the roller motor even for no reason other than the noise. The extra weight that you get when topping off the tank to the full 32 liters is a small (and hardly noticeable) price to pay for the ability to go to remote areas without concern.