I think this update was mostly to have same UI on tablet and phone.
And it always amaze me how people keep telling that after update everything is quicker and faster and smoother and not lagging like ti was before. But...
1)If it smooth on update X and lagging on X-1 update, how the hell when X+1 introduced, suddenly X is lagging one? (this loop is not logical at all)
2)You know that update restarts your phone and as well probably optimize few things(btrfs and so on) so it would work better for sometime as it's kind of "fresh install" =)
As about UX. i see someone compared here to Apple introducing pitch to zoom and as it was not something intuitive. But it was, because it took you 1 second to understand and get used for it. It came naturally and that's what UX about.