it seems to be obssessed with evaluating the effects of 8 week MBSR courses on (fill in the blank: anxiety, depression, test scores, OCD, compassion, flu, etc.). The problem is the first 8 weeks are often a honeymoon period and tell you very little about what to expect down the road.
This is very true (and from the point of non-beginner practice, unfortunate). Though there are good reasons for that: MBSR is very much standardized and has a lot of academic research backing; you can compare with the studies already published; given its reputation in completely secular circles, it is easy to get people to participate.