After hearing good reports I played at 4Grinz for a few weeks, almost exclusively on various Blackjack games. I had some luck and found myself with 3BTC profit over this period before finding myself unable to log in.
I contacted their live support where I was told that my winnings had been confiscated. They accused me of "suspicious" play (which I assume is their language for somebody winning!) and basically told me to withdraw the deposited amount and go away.
I sent them a message complaining about this, I've done absolutely nothing wrong, broken no terms , simply had a nice run of luck so to confiscate the winnings feels tantamount to theft but received no further reply. If they are unable to cope with paying such an amount, then I worry for anybody else playing there and feel the best course of action is warn others away.