Before the inevitable "Argh! They changed his backstory! It sucks, they suck, everything sucks!!" replies...
I wanted to get a word in edgewise and say how much I love this new background for Graz'zt. I think it wonderfully ties in the 4E cosmology with his classic personality and methods. Honestly, I've never been a huge fan of Graz'zt, but that may start to change pretty damn quick based on his 4E vision.
Love the backstory, not too keen on the art, though. Ralph Horsely does good work, but this Grazzt looks less than impressive, and the teeth hanging over the lower lip don't help.
In before the inevitable "OMG I love this, Graz'zt sucked before but now I want his babies!" replies... Or not. Drat.
Well, lets hope that the 4e MoP has more flavor text than that preview, because whatever material it comes up with for the 4e incarnation of Graz'zt, it has enormous shoes to fill when compared to the Demonomicon entry on him that James Jacobs did not too long ago.
As it stands, the flavor is pretty darn sparse. The stats wouldn't be of much use to me regardless of edition, and the backstory doesn't really impact me because I'm not using the 4e generic cosmology. Good ideas I could lift even if from a completely different cosmology and effectively different character, but there's nothing meaty (or fluffy if you prefer) in the preview.