Five stars for effort, for friendliness and for willingness to make changes... but performance lacks
I would recommend FastFields to anyone based on (1) the actual product, which works really well, (2) the friendliness of the team and (3) their willingness to work like crazy.
Where I had an issue was in the actual performance: I sent what I needed in the survey and got back, first, a survey with some logic that I had not requested which caused trouble for some of the info we needed. The second version which eliminated the logic, then hid 3 different address fields we needed. The third version corrected that but I never got an explanation as to why the fields were hidden or who hid them.
This is the second time, however, that I am a FastField client, so I think that the pluses outweigh the negatives.
One thing I would recommend is more frequent communication with the user before releasing the formal product.