As long as it’s done early enough, I’m perfectly ok with that. It’s easy enough to know whether one’s bag is legal or not, and frankly, some of the stuff people try to bring on-board absolutely belongs in the hold.

On the other hand, I really dislike GAs forcing (in often cases subsequent) sizer checks during the boarding process. It slows things down substantially and, as far as I’ve been able to observe, rarely results in bags heading to the hold.