I really don't like it, and for one big reason:
A lot of the pages in my speed dial don't set a favicon. This is true at home to some extent, but especially at work where I have internal pages or HTML files on network shares in my speed dial. With the OLD speed dial, I can quickly figure out which site is which, and the page TITLE is shown prominently if two sites look too similar. With the new speed dial, all I get is a meaningless icon with a snippet of the URL. This does NOT help distinguish between two sites.
It's even worse when two sites have the SAME favicon. For example, I have two separate Google Groups sites in my speed dial. The new look is useless for that.
I LIKE the look and feel. But replacing thumbnails and text with icons is not helpful at all. For now there is a "return to the old speed dial" button, but it seems like something not planned to be supported indefinitely.
PLEASE provide a setting to bring the thumbnails back to the new speed dial, or at least support the old speed dial for as long as you stick to the "icons only" fad in the new speed dial.