Played extensively with a Nexus 4 yesterday. I am ready to order this device.
The smoothness of the OS is now certainly on par with iOS. I tried my hardest to make it stutter. Loaded up a ton of apps, tried to quickly switch between apps, tried to quickly launch things after a swipe, or hit the home button right away, or try Google Now while it's running something (the swipe up from home button to access Google Now is so much faster now), typing extremely quickly... just really trying to put the device to its paces and to see if it would stutter anywhere. It didn't fail once. And I don't know how anybody can try to continue arguing that the touch response is slower than iOS. It was extremely responsive. Pinch to zoom, typing, swiping, launching apps, everything registered right away and felt instantaneously.
And all this, while running a live wallpaper, which I hadn't notice until half way through messing with it. I personally don't like live wallpapers, but imagine without.
Just one more thing Android is encroaching on iOS. The excuses to switch grows ever shorter.