And you're right. People won't leave Google over this. But Google has done extensive testing on page speed in the past and measured its long term impact on pageviews per search. I'd argue that a change in scanning patterns like this one affects the perception of speed of the interface and might impact the aforementioned metric.

Overall, it should be a change for the better and i'm sure that Google wants to increase the efficiency per search to increase the overal number of unique searches a user might do -- while caring a bit less about the number of pageviews per search.

As for Bing, in interface design for a company like Google --a company that effectively dominates the market and sees marginal loss of users-- the competition is irrelevant. Especially for simple UI changes such as this one.

When doing a change such as this one Google is its own competitor. It needs to find a way to transition their user's habits to what they believe is a more usable one. This is by far always the hardest part and really what we are discussing right now :-)

It's awesome to see though. I'd imagine it's incredbily hard to convince a board of such changes, especially in an engineering minded company such as Google.