A while back I did some testing and came up with the conclusion that the true visible title length rule is 512px. This is strongly supported by the fact that the css on search results crop the title at 512px.
Now, Google is rolling out larger title fonts. This means more pixels per character and therefore less characters will fit in the designated title space.
This is currently showing up as formatting issue in the new search results. Titles are currently being cropped mid word as the title text is now too long to fit in the 512px.
I suspect, once the new look is fully rolled out they will update the title text generator to make titles that fit correctly.
I will then have to update my own SERP emulator tool.
And to all those people who sculpted their titles to fit nicely. Sorry.