I rock 40mm tires on my rigid MTB-style-hybrid commuter and it's like riding a cloud sometimes. I put 45 PSI front, the minimum recommended by Schwalbe, and 60PSI rear since I have pannier and often carry groceries or other cargo. It's definitely slower than my cyclocross bike turned road/light touring bike with 28mm tires, but I think it's more riding position and geometry than anything else.

I'm talking maybe 20s slower through 3 miles +200ft, according to Strava, going all out on my road bike vs commuter with fenders and maybe 10 lb in one pannier. So my commuter isn't that much slower, though it does feel more sluggish maybe because the wheels and tires are heavier.