I am finally able to comment more, I have had various issues and not ridden a lot.
It's way faster and smoother. Not sure how much the slip on added and I don't mean power, it just feels more nimble because it lost so much weight from high and to the rear.
I nearly had it get away from me last night. I was passing 2 cars on a country road (individually). Went around the first guy, no problem. Stayed in the left lane to see farther so as to decide if I could make the 2nd pass. A car popped up over the hill but it was a ways off, so I could do it but I needed to be aggressive. I was doing maybe 60 or so, in 3rd gear, so I was right around 5k or so, square in the meat of the power. I pinned it and it accelerated so hard from just behind the truck to in front that I had to really get it over and get on the brakes. The person I was heading towards was an old lady, it turned out, so she was super cautious and pulled over a bit. Also, I think that my headlights influenced her a tad as they are 55W HID and are 'surface of the sun' bright. But it turned out riskier than I had planned because of the level of acceleration, it reduced my closing time more than I expected. The road was crowned too, so the whole thing went from 'fun pass' to 'sketchy pass' in a hurry.
The true test is Sunday. My riding buddy/road trip pal has a 2011 Multistrada. We rode together maybe 5 weeks ago, way warm for that time of the year so we blew off things we should have been doing and rode 200 miles of twisties. This is all pretty far out in the sticks and it's between cornfields that are not up yet (getting to the twisties), so it's an ideal spot to drag race. We raced multiple times, all rolling in first gear at moderate rpm so that getting off the line wouldn't come into play. We must have done it 5x, from 15 mph to 100+, dead even every single time. Somebody got a bit better jump each time but once we both got to WOT, the gap never changed. So we ride this Sunday, same roads, we'll see how it does. This really is the best test imaginable on how much top end difference the flash made.