The functionality is still there, but they've made it harder and harder to access. It used to be an obvious choice. Then it was buried in options, then deeper in options, and now I can't even find it any more. However, if you add the magical "?sk=h_chr" to your Facebook bookmark you'll get a chronological feed (at least until you click on the icon to go back to the top so refresh instead).

I'm sure they'll completely break it some day. They broke it briefly once already. Since I was working at Facebook at the time I filed a task on it. The response was the rudest I ever got in 3.5 years at the company. If it works, as long as it works, it's basically by accident (or because some front-end developer is resisting management's constant pressure to deprecate it).