Probably more comfortable than older style shirt stays.
I've never worn one in my life... frankly had no clue this was even a thing!
Looking them up, all the standard ones seem to clip to socks. But I've also seen that with thin pants you can see the straps. That's not cool. Funny that the Marines appear to basically stress the use of them, but not once did I ever hear about shirt stays through anyone in the Army. Damn them. My body shape/size definitely leads to billowing with more shirts than not, it takes careful shopping to get even slim shirts to fit me without looking like shit.
I... actually really want this.
It's on kickstarter. I was bummed to find that out, and they aren't expecting to ship until June. Dammit, that's not now!