I'm inserting an argument into the visual editor using tiny_mce_before_init and it works as expected in 3.4.2 and lower, and on initial load of the editor in 3.5 beta 1. However when I switch to the "Text" tab and then back to the visual editor, it appears to be initializing again while ignoring that filter.
Should not functions applied using tiny_mce_before_init hold on every instance of the visual editor, not just the intial page load? The current behavior in this respect is inconsistent with 3.4.2, which I believe is correct.