I use it for normal contact forms and for order forms. Anything where people do not need to register to submit something to me, and I never got any spam through the BFF.
It is quite easy to set up (I'm not a programmer), and Phil has been very helpful and sometimes even done on-site-editing to make the form work, when I was a newbie in Joomla!
The forms are very neat and flexible in function.
If all extentions were as excellent as this, the whole world would use Joomla :-)