When someone asks you how far you are gone with doing something, how it is going and you want to express,that everything until now is going well ,you use this idiom.
"So far, so good."
It refers in general to a satisfactory feeling about an existing condition.
- You have been living here since a week or so, how do you feel in the new city ?Do you like it?
- So far, so good.
It means here everything is alright up until now.