Surprisingly, not as much as I would have expected moving from the summers. These are not as sticky, of course, and cornering I can feel the difference, but I've not noticed spin from launches. That said, two things: (1) with the summers, it was like glue on the road, I do miss that a little bit and (2) I haven't had a ton of above 60F days to try out, but I've been very happy with the (slight) dropoff from the summers and the increased confidence during our cold and snow here.
I still have my summers (only 250 mi on them) and am seriously debating whether I put them back on in May or just keep the AS. I will probably swap back at least once (why waste basically new tires) but I haven't noticed a real drop off with the AS 4 and that was my argument for going AS instead of pure winter/summer setup. Might also get another set of Arachnids and hold the summers for track days or something.
Side note (or, perhaps, back on topic!) I received the flaps! Thank you
@M4H4X - I'll be putting them on when I get a chance.