Initial reaction, I'm on the fence with a leaning towards disliking elements of the implementation but an overall view (or hope) that it's very positive. In theory it should be a great addition, but there are just a few too many unknowns for the moment for any of us to be sure.
It's going to be very difficult to judge it properly until we see the uptake by users and the impacts it actually has on SERPs. From the outside, it appears as if it's a reincarnation of their old attempts on the back of the FB success of 'liking' (which has introduced a mass userbase to the concept), but instead of it being confined to mindless humour it has a direct benefit to our social circle. However it's a very different tool with a much greater social disconnect at first glance, in reality it's actually a far more beneficial connect, so gaining traction with it is the key. Given the integration with so many of their existing tools, they should manage this without much trouble.
Google's attempts via Buzz (and the resulting FTC issues, ironically announced today), Social Circle, SideWiki, starred results, chrome exclusions and now moving to +1 show a slightly confused and disjointed approach to integrating social signals. Looking through the requirements for someone to be included in my social circle, it's a pretty poor representation of who I actually want to see information on in results so I'm still not sure they've completely nailed it. It's definitely a move in the right direction, but not the final destination yet.
