The Verge quotes Microsoft sources claiming FM radio support in upcoming WP8 update. General Distribution Release 2 (GDR2, Portico was GDR1) is supposed to add FM radio support to Nokia Lumia 920, 820 and other compatible phones. Looks like the registry keys were there for a reason.
Verge also mentions Nokia-specific GDR2 updates: double-tap to wake the device from standby, flip to silence option, color profile settings for the device screen.
The update will be made available over the coming months, I assume before Google ultimately turns ActiveSync off for WP users on July 31st.