I like the idea that this is backed by a service that has an API that can call out to other APIs. It has an "app store".
I think you can sign up for the SDK already: https://developer.amazon.com/public/solutions/devices/echo
It's one of the only devices in my home I use as often as my cell phone.
I look forward to the day when I can push information back to the echo using apps like tripit:
"ranman your flight is leaving in 2 hours, should I call an uber or give you the train schedule?"
"It's lunch time, want to see what's in the neighborhood you haven't tried recently?"
"You have an incoming skype call from X"
"Welcome home, want me to turn on the news?"
The only downside is that it depends on always on and fast connectivity.
I'm not particularly concerned about the privacy of it all (I do recognize the concerns other people have) but I would be interested in learning more about how the privacy is handled.
The other interesting device in this category is the Jibo: https://www.jibo.com/ but I haven't seen any of the details on the developer side of that yet.