I have mixed feelings about funnel analysis. Looking at my games, would it help me if I know where exactly problem is? Unlikely, poor games are poor, good games are good. The games I would want to use funnels for are already too broken/poor for it to make a difference. Besides, would knowledge where the problem is tell me how to fix it? Unlikely. Most things can be checked better by keeping in touch with players anyway.
Funnel analysis would be useful in rather few cases. Like feedback from new people (who quit before finishing tutorial) or like some warnings set up for basic things (for example if registration system did not broke down due to some changes I made in the code).
If I already had funneling analysis system I would probably check it from time to time (mostly out of curiousity), but if I had to write it I would find it a waste of time.