I use them, the interface is a little dated and they make it hard to know what your balance is. The casino, sports, and horses are utter shit, but you get poker action. I don't take bonuses so I have no idea how that works with them. Not the best poker software, not the worse.
The software has got nothing on Pokerstars or Full Tilt, but it's decent enough. As a U.S. player, ACR has been a solid place to play. Unfortunately, there are really no Omaha games available, but the Hold'em ring game liquidity is okay and I like the MTT schedule as a low-mid stakes player.
It was a bit of a hassle withdrawing via Bitcoin (required email/phone verification and I had to go find my last deposit info), but I got my funds out within a couple days.