I have played PKR a good deal. I was one of the early beta testers.
If it doesn`t work for you, it is likely because you are trying to access it from an IP address in the USA (it is not open to Americans), or because your PC is not beefy enough (it needs a fairly high spec).
Graphically, it is the best there is. However, I must admit I seldom play there any more. Their tournament structures are much too fast for sensible play and, since I am largely a tournament player, no amount of prettiness compensates me for that rather significant defect.