Definitely seems interesting, though as staunch said, the barrier to installing a new plugin is significant.

I wonder how Google feels about the widgets covering up the Adwords ads in the right column. Enough people start using it and that could impact their revenue. Is there even anything they could do about it? Maybe they would acquire the company, or just clone the best advances in search interface for themselves.

I also wonder if some of the widgets might be redundant. Wikipedia and YouTube, for example, are already heavily represented in search results. In the screenshot TC posted a few results are duplicated.