I saw one on the bike trail last weekend, looked cool.
I always kinda preferred the bike trailer to a cargo bike just because then it's removable. but i guess if you'd want an electric assist, the cargo bike would be a good platform
We used to ride my daughter to daycare in a trailer, I'd clip it to my bike, drop her off and lock the trailer at her daycare/school. then i could ride in without the trailer (or without a big cargobike) and my wife you pick her up, clip the trailer to her bike and head home. it was a sweet setup.
I often consider digging into an electric assist on a bike but it's sooooo expensive i just can't justify it. like that surly is rad as hell, but it's also more expensive than every car i've ever owned combined...