Went out today in hot and muggy conditions with the TT helmet. This is a much better solution than sunglasses. The screen is vented and seemed to direct the sweat away from eyes and the windscreen stayed clear. With sunglasses they are covered in sweat within minutes and basically useless, I use Oakley M frames FWIW.
I've been so conflicted about visors. I have a LG Rocket and after watching Garmin, whom I consider to be technically savvy, show up at ToC with visors I decided to get a one. In passing, I mentioned it to a buddy* who has spent many, many hours in the wind tunnel, who said, "Stay away from visor like they were the plague." Bummer I thought. Later, I ran into a very credible aero person * on a local ride and I asked him about visors, Garmin using them, etc. and he said that it's of course variable to the rider, but that perhaps they did tunnel testing at 0 yaw, and the problem is that at other yaw angles the wind can come up under the visor and make a "parachute" out of it. Of course this is dependent on the rider's face and how close it is to their face. If it's close then it's usually ok. So I tossed the visor in the closet and haven't thought about it until your post. I then thought about it some more after a local TT in which I was annoyed with my M-Frames. So I pulled it out and installed it on my LG and it fit very close to my face. Perhaps I'll try it in the next TT to see how it works compared to my M-frames.
* Names protected because I asked in a conversational tone.