Turn lights/switches/home-automation stuff on/off.
Read stuff from Audible.
One command music streaming. (Google Now will bring up a link for you to click)
Shopping. (Reorders prime items from Amazon)
Coming Soon:
Integrates natively with all sorts of apps - (There's an SDK in the works)
Wouldn't it need you to buy compatible devices for the home automation to work (If yes, the phone would do that as well - there are 'app' controlled lights/other fixtures).
And Google Now does do one command music streaming (I do that everyday - "Ok Google, Play Music" - and it starts playing). Audible and Reordering past Amazon orders - Some people may find value in that. I don't listen to audio books or reorder stuff in general from them.
Coming Soon: Integrates natively with all sorts of apps - (There's an SDK in the works)