I would never do this for a website or web app, but if they could make it code emails that work in every email client I would use it immediately. I don't care how shitty the code looks.
It's a neat idea. It'll be a lot of work to get right. In the meantime, I can send a psd, png, whatever to cssilize and have it chopped up by a human into great looking html and images and I don't have to piece-meal the psd myself to conform to what markupwand needs:
I don't understand how people are still designing for the web in an image manipulation application. There are so many other tools out there today to get you to a design much quicker than Photoshop.
Photoshop and Fireworks are great and I don't see many designers abandoning desktop software entirely. But I think there are plenty of tools that can help you get into the browser more quickly.