Overall Classcraft has been quite successful with the classes I have used it with.
Most find the mechanics of the platform engaging and like the consistent positive reinforcement that they receive. The gold coins also create a good opportunity for class auctions which helps to make rewards tangible. I tend not to use the heart system as I would prefer the whole experience to be really positive, so I use the school's behavioural processes instead when there are any concerns within the classroom.
How I Use It
I used Classcraft primarily as a form of positive reinforcement and a way to provide some autonomy to students in my class through the use of quests. The group mechanics also enables healthy competition between students to be fostered.