The changes are obviously intended to improve user experience across Google products. Another obvious consequence of this change is relevant ads across all of Google properties.
Algorithmic usage tracking is a common industry practice. Most internet based firms/websites use tracking software. If you are an Amazon user, you would have surely noticed targetted ads to buy various products from Amazon purely on the basis of your browsing behaviour. By the way, on the internet, every click (that results in a http request) gets registered on multiple servers and is likely being used by the respective service providers. Google is only being transparent about its changes in terms of service.
The tail piece: Since, the changes took effect my search experience has notceably improved. For instance, I was looking for information on ways of installing Android 4 (Ice Cream Sandwich) on my intel x86 PC and then I found the most relevant results as the first link on the search result page (even though they came from an obscure blogger). Thanks to the search engine, I was able to install Android on my USB drive and run it on my PC.