First, it is important to note that this only affects users that are logged in. A few months ago I wrote about the dreaded (not provided) keyword and found that 4-9% of users were searching will logged in (at least on our sites). Since then Google has announced that they have over 90 million active Google+ users so I would imagine that number has already increased and will only go higher as more users start finding value in Google+.
Anyhow, back to the matter at hand. Just how different is the new search? Well, not very unless you want it to be. Google did a pretty good job of not cramming down our throats this time. The changes are subtle is you don't care to see the customized results or radically different if you do. I ran a search for "us airways" both logged in and not to see what all the hubbub was about. I was a little surprised , but here is what I found.
1. Google+ only. This was a bit of a surprise and Google has taken some heat for this. However, I would remind everyone that Twitter had a deal with Google to index their results up until last October and Facebook has actively prevented Google from indexing their content. Both sites use robots.txt and rel=nofollow extensively. Both have been invited to the negotiation table by Google and Facebook does have a deal in place with Bing, so I expect to see other networks represented in Google search results soon.
2. New header. In the logged out search, the top of the page just had the "Search" title and the number of results. In the logged in search, I now have some icons of users I am connected, a link to the personal results found, and 2 buttons to allow you to toggle between showing and hiding personal results. hiding the personal results changed the page to look like exactly the same search results I got from the logged out search.
3. Google+ link. The next obvious difference was the new link at the bottom of the page inviting me to ask for input from my friends on Google+. Clicking the link brought up a lightbox with a form that posts directly to my Google+ stream.
4. Personal Results. Clicking the to see all of my personal results did exactly what you would expect - showed me a bunch of people I know talking about how much they hate US Airways. Not very good for US Air, great for me if there was any doubt about what airline to fly.
5. Search listing. This one was not as obvious as the other changes and it took me a little while to notice. The actual search results were slightly different when I had personal turned on. The #9 result was actually a link to a blog written by someone I am connected to. Presumably, the more relevant the results, the more likely that personal results will be permeated through the actual results listings.
What does this mean to you as a business owner trying to get in from of searchers? Well, it means you have more to optimize now. You will have to pay attention to social networks now more than ever. Personalized results will be the way we search in the future, after all haven't we always known that consumers trust the advice of their friends more than they trust our marketing?