I went for my first and only time three years ago, mostly because a bunch of my friends wanted to go and kept encouraging me to. It turned out to be a LOT of fun--at least in part because I went with friends. If anyone knows what it is, I was part of the EJB crowd.
But the event itself was quite entertaining. I've gone to PAX East before, because I live right next to it and my OH likes games (I don't really care for any games anymore... other than like Solitaire or watching friends play something rather than doing it myself), but it's definitely an entirely different experience. PAX East has so much--too much really--and it's all a big jumble of games, people, presentations. Blizzcon is very well thought-out, doesn't feel overwhelming, and there's always something fun to do. I liked the art gallery and the sessions with artists sketching in real-time.
I wish I could go again, but I'm afraid it was a one-time venture, and I haven't dabbled in WoW for quite a long time now, so I'm mostly out of touch. It's also quite expensive to travel across the country for a few days, plus the Blizzcon ticket, plus hotel. I have some nostalgia for those old days when I would have been overjoyed to go. Anyone who does go--have a great time!