Let me preface this by saying that I don't consider myself to be part of the anti Search Plus Your World crowd. I think it has its pros and cons.
I will say that I don't like when it leads to Google serving me less relevant results (which I think is happening more as a result of other algorithm tweaks as well). I searched for "mark zuckerberg" and Google returned me his Google+ profile as the very top result. Not his Facebook profile. His Google+ profile.
Any guesses as to how many Google+ updates Zuckerberg has shared publicly? Zero.
Any guesses as to how many Google+ updates Zuckerberg has shared with me personally? Same answer.
So how is Zuck's Google+ profile supposed to help me as a user for such a general query? I don't know. Perhaps Google is delivering this result because I do have Zuckerberg in a circle (in case he ever does make an update). I'm not sure, because when I try to test this by taking him out of the circle, Google doesn't accept the removal. A bug I guess. Either way, if it's because of the "personal connection" between Mark and myself, does that mean Google's algorithm isn't sophisticated enough to realize that there is virtually no content on Zuckerberg's profile? Isn't that against the rules of search quality, which Google has driven into the ground since the unleashing of the Panda update in 2011?
Of course it's sophisticated enough.
Isn't it also sophisticated enough to see that Mark and I have never actually exchanged a piece of information with one another via Google+?
I don't want to get into all of the talk about Google's competitive practices here, because that's not the part that bothers me as a user. It's the whole making the results less usable thing.
As a Google user, I want integration among the various Google services I use. However, sometimes Search Plus Your World benefits the results, and sometimes it does not.