Yes got a set of these, being using them for the past four months and no complaints. Those people that actually want to speak to us for a valid reason are happy to announce themselves (after which you can add them so not challenged again) and those that just want to spam either hang up or end up getting auto blocked.
2. There are always several idiots that can't be bothered to follow the simple instructions when they call you and just hang up at the start of the instruction message. All they have to do is announce who is calling. It's not that difficult!!