It's great that Mozilla have woken up to value of tracking in deliverng relevant content. However, this is the browser that decimated targeted advertising revenue for millions of websites by leading the 'do not track' charge.
Tracking was the best tool we had to deliver a better experience. Privacy concerns needed addressing, but they used a sledgehammer to crack the nut. Between Do Not Track and the utterly ridiculous EU cookie law, many users now see all tracking as some nefarious attempt to invade privacy and are scared of cookies.
I'm still using Firefox, but only through inertia. For a long time it was the best browser available. This hypocrisy is just the motivation I need to move on.