Another MS company has offered these in the past and I did the census 3 years in a row. It is a lot of hard work. The original company paid $12 per hour from the time you left home till the time you returned PLUS a gas allowance. I read what GFK was offering and said "no thanks!". Also the original company used booklets which they mailed to you and you had to return, postage paid. This one requires a tablet to enter the data in real time.
In all fairness I did do one "segment" that was actually one square mile (in Mesa, AZ); however, I accepted one in Melbourne, FL that ran about 7 miles long and only a quarter mile wide. It made walking the segment impossible.
Based on what I have seen regarding payment. I would run!