The guys at dpreview say that it's about half the thickness of the 50mm f1.8 That's insanely thin!
It has a 7-blade aperture, don't know if it's rounded, but it probably will give you much better bokeh than the 50mm f1.8. All in all it does seem like a very interesting lens Albeit it must perform extremely good at f2.8 otherwide the price-difference will be too big I think.