That's a very good strategy - testing new features by controlled rollout so that their potential revenue impact can be fully analyzed. Every company that lives on profit should adopt that strategy.
It's the reason we still have the Google Black Bar when they highly publicized a new navigation last year. It hurt traffic to their other properties.
I like the black bar. It is simple and it works.
I don't hate it, but if you have a nice new tab page (i use speeddial 2 for chrome (and I have a link to calendar and drive)), I don't imagine someone using it that often.