But here's the thing: this actually lifts the lid on the echo chamber to be more open than it was yesterday. Google recognizes that global search is a necessary option. Before this update, it looked like G+ was just going to be rammed down every Google user's throat. Now we can opt out without having to log out!
I agree with you. Prior to this, the only way to get global search was to add &pws=0 to the URL. Now, it's a button. It's a big step forward, and not that I don't like the "bubble", it has its advantages (increased relevance). It's fantastic to be able to switch between the two modes at the click of a button, and it's something we didn't have before.
It's not just a button, either. You can opt out entirely from preferences.
Further, the ability to swap back and forth between personalized and unpersonalized views makes the differences visable to users in a simple immediate way, so we can each make our own mind up about the tradoffs between relevence and "echo".