This all sounds really weird, like there's no consensus on how the kobo behaves: Kobo1 was slow, then got faster with 1.8 - Kobo1 was fine, then 1.8 screwed it up - Kobo2 takes three seconds to flip page - Kobo2 flips page in under one second...
So, windows, I don't think you're the only one who's bothered by the slow page turns- there are others who've mentioned it before- but not everyone with the same kobo and firmware as yours has that issue. Wonder what's going on.