The entity resolution does appear to work quite well. I searched for common names, like John Smith, and although you get back a ton of results, they all seem to resolve. The easy-to-use advanced search (it’s barely an “advanced” search) helps with things like location and age.
One apparent primary source of information are networking sites, like LinkedIn. Neat idea. There’s also user-entered and generated input that feed into the entities. But right now it seems to work best for well-known people, particularly in displaying photos. Most of the time you get “no image” placeholders shown.
Here’s my page on Spock. Doesn’t look like there is anything to be found for Jim Kalbach, so I’m not sure how well name variations are handled. One cool (and scary feature): you can have Spock go through your Gmail account and add people in your contacts as favorites in Spock.
The interface design is simple, with lots of text links, in the style of Google I’d say. Looks to be a good service, but it seems limited to me right now.