To answer that question.....
The person I've seen on it in real life is the lady that's a sales person at the Trek store who does ride frequently and leads a Trek sponsored group ride. She was on it on the front of the sponsored group ride.
I was heading down a long shallow hill and passed the group. They were pretty "Fred" heavy on that group ride and she had them going down about 28 mph in her draft. Maxed out. Sorry, no other way to put it. When you wobble a few feet left and right in a line, you're a Fred.
Looking as I passed by, not a single one of those dudes I'd want on my wheel at 30mph on that road.
I still think 350w "could" be a lot. 350w matters as to weight and the aero position of the rider. 350w on a granny Dutch with a 300lb rider ain't nothing fast.
Around here, I can get up a 4% hill at about 20mph hitting 350w manually. In the flats, that's good for 30mph.
The other people I saw had the slightly slower but just as powerful MTB version of that Trek. A dad and his probably 120 lb 12 year old son cruising the greenway.
120 pound kid with maybe 150w of manual power max and then 350w on top......that seems like a bright idea.
I do agree, most commuters and users are going to be on a budget and likely only own something with much more modest output. But, I have seen them in the wild. Picking up parts recently at the shop heard them talking about they had sold like a dozen of them in a month.
FWIW, I climbed Mt. Mitchell at an average of only 150 to 170w when I was about 180 lbs. It wasn't pretty, it was slow, but it worked. Less than 200w.
You only need like 170w in the flat to go 20mph. 170w is plenty to ascend most American hills in "anywhere USA" town.
350w is more than double that. I dunno. Just seems like a bundle.