Yeah... the utility offered needs to be super compelling to outweigh the weirdness factor.

I think that's partially the genius of something like Alexa (and eventually Google Home). You're in your own space so you're more likely to feel comfortable blurting out questions and commands.

How is it any different to talking on the phone?

In the early nineties only yuppies had cellphones, and people laughed at people talking on the phone on the street, bus etc.

Now it's completely normal.