Yes I know lots of people like them, hence I took a replacement of the first broken one, but it must be the way I use it, and the second one broke too. The plastic just snapped at the shoulder first time I used it. I’m just too strong, I guess!
There is a metal screwpull now - it weighs a ton by comparison with its lightweight plastic cousin.
I replaced my screwpull, not because it broke but because the teflon had worn off the screw. I think the secret to avoiding breakage is to hold the legs firmly so they are not forced apart by the downward reaction force against the bottle itself.
The button is in the Pull Parrot video in @robert_mcintosh 's post. You push the button to pop out an edge that that gives leverage to the early part of cork removal. It is like a standard waiters friend with the addition of the button.
The broken arm version replaces the function of the button with a hinged lever so you use the shorter part of the lever for the first pull of the cork, and the longer part for the remaninder. This type is becoming increasing popular and they do a good job.