Lees and answer emails, send messages, and I imagine that the default whatsapp at least let you use siri as keyboard input. Currently integrates with iMessage, remember.
Currently in English, but come on, I think it is the best voice recognition / interpretation of natural language to date.
You can also do something I think is just amazing, its integration with Wolfram Alpha
Anyway, I only see him a utility: when I get up very early morning at 7.15, and to go asking the time, mail and stuff while I try that coffee wakes me: D: D: D : D
(of course, to see who is the handsome understand my voice in those conditions lol)