Delayed response - My main uses are simple things like asking about the weather (current and future), listening to the flash briefing and asking random things while watching TV, asking what's on the family calendar. Had it hooked up to a smartthings hub for a bit, which worked, but the smartthings platform has issues so I've abandoned the idea of smart home control. Will buy a Philips Hue system in the next few weeks.
My wife, who hates gadgets in general, likes it in the kitchen to add stuff to her shopping list while cooking (with messy hands). In the store she opens the echo app and checks off everything on the list. It seems like a silly thing, but she thinks it's terrific and it has saved us many useless return trips to the store. She also loves the option to play music (again, for the same reason, messy hands or just busy).
My 7yo uses it for music, to get the answers to trivia and interact with a few 'skills' I've enabled (guess the animal, etc). She also "plays with Alexa" when friends come over (they take turns requesting songs and dancing)
The echo is not ideal, especially in terms of underlying knowledge base, integration with other Amazon devices (we have two firetv boxes, amazon owns IMDB, mysteriously neither are well-supported or integrated) and the "skills" approach is cumbersome (should have used an "intent" approach instead of "ask {skill}"), but voice recognition is better than anything I've used and it works for everyone in the family without training, as well as random guests, including kids.
PS I signed up early and bought it for $99, a second one was requested, but I feel the regular price of $179 is too high with the current feature set.
Note: It does NOT (yet) allow handsfree calling. I wish it did.