I played GW for a while with some friends of mine, and while it is enjoyable, it's not nearly as good of a game as WoW, imo. The GW campaign can be enjoyable, and every once in a while I have fired it up for a day or two. The graphics are indeed awesome (and come to think of it, now that I have a new computer/video card I should give a look see). I like the class system for the most part, very strategic and creative approach to class design.
Once my friends started to move onto other games, my interest waned. I normally am not a big fan of pugs, and imo pugs in GW's campaign tend to be less enjoyable (not really sure why) than most online games.
Your milage may vary, so if you can borrow a friends account for a few days and give it a go I would say it's definitely worth a look see.