Nothing. Doesn't affect me one way or another as long as they're riding with the same courtesy we'd expect from any rider, and show to others.
I was passed for the first time by an ebike a few weeks ago. Only reason I noticed was because I was flying at one of the fastest paces I've managed since resuming cycling in 2015, on a slight downhill grade with no wind -- and was still passed like I was stopped by a fat bike. Nothing unusual there, I've been passed by human powered fat bikes before, even when I thought I was pedaling flat out. Only after he passed did I realize it was an ebike. That was less humiliating than being passed by a human powered fat bike with knobbies doing 20 mph when I was doing 18 mph on my old rigid mountain bike with city tires.
In January I realized a friend was using e-assist bikes only when we rode together and he mentioned it. We'd ridden in casual groups before and the 10-12 mph pace didn't draw any attention. But on our more recent ride we tackled a hilly route on a windy day and I noticed he was passing me easily on hills with a head wind -- riding a heavy comfort hybrid, while I was on a lighter rigid frame bike. He just laughed and pointed to the e-assist mechanism that kicked in on hills and on demand.
I'd consider an e-assist bike if I rode more often in heavy traffic. There are some busy stretches I avoid because I can't sustain a 20 mph speed for longer than a sprint on some slight uphill grades. But having an assist to get through a tricky mile-long or so segment might be helpful and safer.