I would love to use WoW, and the Hero's Journey curriculum, as an after school club (and I have a few students who are totally interested in participating) but it is so expensive. And on top of that there's the weekly recurring fee. It doesn't seem possible to pay all that for an after school club.
I did download and tried Guild Wars 2. It doesn't seem as fun to me as WoW but maybe that because I played WoW for years and I love it. GW2 is cheaper to buy and download unlike WoW that has so many versions if you want to get to level 90 and there's no monthly fee. Lucas Gillespie says that WoW curriculum should work with GW2 (not sure if they're reworking it for GW2 though).
So yeah, since I teach Science for me an after school club would be a great place to start.
I am a teacher in a teachers university in China, so my focus is on using games among undergraduate students. Several years ago, I used Quest Atlantis (QA) in one of my undergraduate course "Instructional System Design". The context was to understand the Instructional Design and Problem-based Learning in game world. After that, considering this game is an English and Educational game, so I used it among 15 volunteer undergraduate students for them to learn English. But, in the end, I thought WOW would be much interesting and valuable for Chinese undergraduate students to learn English. However, the students will have to download an English version of WOW and register in an US or UK server, and there will probably be some lag when they are playing WOW in an US or UK server.