That's really cool. She could be advising and doing things for you just like she does The Chief. Although, I kinda rather have Master Chief.
I used the text to speech functions in Window Phone 8, and sometimes it gets it right, other times it is hilarious.
I wonder if they will bring back Microsoft Home or something like it. So on the way home you could tell Cortana to tell you whats missing from the fridge for a fancy dinner, generate a shopping list, turn on the air conditioning and get the hot tub warmed up to 104F 40C.