Smooth and slick on my iPad; depends on support for hardware transforms.

It's a combination of the blur filter, a huge monitor, and integrated graphics. With blur turned off or the window resized, it's much smoother.

On my old Thinkpad X200 with Ubuntu/Intel graphics.

Firefox 14. Smooth transition lasting about 1 second. The smoothness suggests more than 4fps. The text within the modal window 'jitters' or 'shuffles' slightly after the transition has completed, as if it is kerning or loading a font.

Chrome 21 (stable for Ubuntu/Debian) much less smooth, quite jerky. The font 'jitter' isn't there.

Strange, it's butter-smooth for me on Chrome 21 and Chrome 23 Canary. (MacBook Pro i7)

really? it's strange to you that it's smooth on an i7? If it wasn't smooth on an i7, what would it be smooth on?

Older version of Chrome was the strange part. I was assuming effects were getting offloaded to GPU.

I liked the concept a lot, would definitely use it... but on Chrome 21 + Windows it's really, really slow, looks like it's rendering a 3D model.

Seems smooth on a galaxy nexus with chrome 18