Stunning game. Worth every penny. Be warned -- it may ruin your life.
I've been playing it on and off for nine months, and am still as compelled to go back to it every day as I was when my first Troll stepped onto Kalimdor.
I've got one character at 60, and am now starting another on the other side on a different server, and it's only on the second run through I've realised how well-designed the game really is.
It's not faultless though... the live code is unacceptably buggy since Blizzard do not have a good enough QA process for patches, and sometimes one feels they don't do enough to keep the current system running properly, but overall the game provides an unrivalled playing experience.
Buy this game, but don't expect your life to be there when you get back....