In 3.4, you no longer need any PHP to customize the defaults for start of week, feed language, or default timezone. (You would have hooked into populate_options for these.)

start_of_week and timezone_string/gmt_offset are now translatable, and rss_language is gone (it uses the site’s locale, now).

I’ve created a page here that outlines all changes to 3.4 so far, including the details for how to set these defaults: Important Changes for WordPress 3.4. I will update it as more changes happen.