I am currently a student there, in fact I came in the fall of 2009 for a few weeks and returned late last year for an extended stay. I think it is an excellent school and the teachers I have had have all been really great. I have only taken the 1-on-1 classes but they also have small classes (I think 6 or 8 students and one teacher). Those are cheaper and maybe good for someone already living in Kunming and busy with other activities, but for me 1-on-1 is far better.
As I am staying there for an extended period of time they sponsored my Student Visa which for me was fairly hassle free (well, ignoring the medical exam).
As for the price, it seems OK to me. But as with anything you'll have to weigh the cost and benefits based on your own needs and targets and of course it always makes sense to look around before jumping into anything regardless of how good someone else thinks it is. It also makes sense to first visit the school in person before deciding if at all possible. Unfortunately that is not really an option for those not already in Kunming.
Of note, they have a number of students who have returned to the school multiple times over a few years, so they must be doing something right. But of course, everyone's experience will be a little different based on how well any particular school suits.