Seriously. Incredibly lightweight, nice action on the locking sleeve, and the nose and top bar are small enough to clip even the most crowded bolt anchor.
I climb with 6-8 of these and use the for every locking job except on my belay device.
I've got a few of each of the main brands of wires in my rack, but I still find these work best.
The only problem I have with them is that the really big sizes (12-14) sit a bit too well in good placements. It think it's because there's a bit more flex in sides of the nut, and I do tend to really yank these things into place.
As a result they can be a real pain to get out. So if you're climbing with a partner who's not great at teasing out passive pro, you might want to be a bit careful placing those big boys.
Still, it says a lot that the biggest issue have with these is that they sit too well!