I don't think anyone actually seriously likes this series, but it is good for some ironic fun. I mean the kind where you're laughing AT the story itself rather than with it because it is a complete train-wreck, and watching trains crash is funny.
Feels kinda weird to think the average rating is about right for a series, as about half the first page of top rated manga on the site are utter sewage. Something in the 6 to 7 region is kinda rare around here... but it fits in this case, at least as far as end entertainment value goes.