Ive been studying at SFL for the last 5 months and have found it fantastic. I originally tried KCEL and found their classes ok but it just didnt have the flexibility I was looking for. Also it was a very generic class just like that of a University back home where you couldnt ask all the gritty cultural questions a foreigner wants to ask living in China.
SFL is well set up to do one on ones or small classes and teachers are actual teachers not just an english major that happens to teach on the side. In my one on one classes Ive had insightful conversations that have lead me to better understand Chinese culture and language more than anything else I have done. I choose my own topics and the teacher then prepares great power point slides to guide the lesson. Thoroughly recommended.