I wanted to answer a few of the comments and explain this in a bit of detail. This ticket was quite a big deal back when it was originally opened and made a lot of sense. If it had went into core back then, it would've been great for plugins like WP SEO because it would've solved one huge problem, which is to get theme authors to properly use the wp_title() function. That's the thing that goes between the title tags in the header. See, if themes don't use that function properly, it breaks the output of plugins that alter the title.

However, there was another way to get theme authors to properly use it: make it a guideline for the theme review team. And, that's exactly what TRT did. Any theme going through the WordPress.org system was forced to use the function correctly. We managed to fix this problem in the three years it took for this ticket to get pushed through.

Now, what does this new thing do? Not much, actually. It certainly doesn't fix the issue that was originally brought up. What it does do is mark a transition in which core WP has total control over the output of the title. It really is best that core WP is outputting the title in the head rather than the theme so that there's no confusion if/when they do something like build a title tag editor into core (yuck).

So, to sum up: this is basically a method to allow core to eventually do something that belongs in a plugin. It doesn't fix any problems.

@Olaf Lederer - No, this offers no current improvements. The new method is simply a different way to add the title tag to the header.

@Marc Connor - It won't change anything with plugins like Yoast's in the least. Three years ago it would've been helpful.