Many students were thrilled right off the bat. It was mainly my group of athletic boys, who are constantly driven by competition to do well. The fantasy/sci-fi aspects of ClassRealm drew in other students as well. It didn’t matter why they cared. I just wanted them to care.
A 6th grade teacher found that participation and enthusiasm for his class skyrocketed when framing things in a different way - that is to make learning feel more like a roleplaying game. There's been lots of studies and tests that have shown that kids learn better in more interactive environments and that they enjoy interactive / active tasks far better than sitting still at a desk.
Unfortunately, as adults, we know that that's a big part of life - learning and knowing how to sit still and concentrate in rather... inactive environments, so school is often used as a way to prepare students for the working world.
Still, I'd be a lot more enthused about working if it was more like a game. Imagine, getting credit for the awesome things I do at work *swoon*