Enabled for new users by default. Existing users currently need to go to Preferences and set the cookie setting to “Block tracking” rather than one of the other options to get these benefits.

tracking protection != ad blocking. the side effect is more like it blocks some 'targeted' ads, but it seems disingenuous to say it blocks 'most ads'.

I'm not trying to be disingenuous. I don't have an ad blocker installed, and except for when I turn tracking protection off because it broke some site's functionality I can't remember the last time I saw an ad.