I have not used them either.
I have not heard about them being hard, particularly.
But I have heard about their quality control being a bit lax and
allowing primers to be produced both too big and too small.
There was no general complaint about primer failures of primers that
were actually mounted in live ammo.
The general consensus amoung the people I happen to know who have used
them is that you will find a percentage that you cannot use and you
have to factor that into the price you pay for them. Nobody has said
they will not use them, but most have said that they always factor in
the "loss rate" when looking at prices.
There wasn't much of a consensus about how many you are likely to
lose. Guess you'll have to make your own decisioins about that.
The primers are non-corrosive but they aren't "Green". I've really can't
complain about Wolf ammo, it goes bang and is typical factory load. The
powder they use is sometimes dirty and sometimes clean, they probably use
different powders from batch to batch. I'll sure find out how their primers
handle in process and since I really don't have any light hitting firing
pins I'm confident they will work in MY guns and we'll see how well they
work in friends' guns.