PC. Don't know how well it is on the other systems, but I don't care to find out. At first I couldn't run it well on my computer, but after I simply unplugged it, I got it to run this, and many other games (like Crysis, etc.) to run at its highest with a smooth frame-rate. I'm going through it now, so sorry if this is a stupid poll to others, it's just since I'm playing it now, I'm thinking about it as well.
360 and also played the game on the PC.
Didn't particularly enjoy either. I loved the story and much of the setting but the gameplay really didn't hold up on either system. I'm a big fan of Baldurs Gate, Neverwinter Nights, etc, but I felt Dragon Age just felt really clunky and even dated. As great as BG was back in the day, I don't think trying to do a modern version of that works. I see it as the equivalent of the Elder Scrolls 5 going back to dice rolls..
I'm very glad they're taking Dragon Age 2 in a different direction.
PS3 - awesome game. There's a little bit of funkiness if you compare to PC but it hasn't really bothered me. This was my first type of WRPG like this so I didn't play it as in-depth as some. Micromanaging just took a little longer navigating those radial menus. Only thing that bothered me was the targeting is junk compared to PC because of the close up view.
PC where it should be played. It was easily one of my favorite games of the past decade, and it makes me sad that they are dumbing it down for the console kids in number two. Everything they say they are doing to "improve" the game makes me shake my head in disgust. They are trying to dumb it down to be more like Mass Effect to make it as mindless as possible and it makes me sad to see them doing it. I hope they don't destroy this franchise.