I ordered an M6-R but was upgraded to P6-R due to a mix-up by
Evans Cycles. Over 7 years later and with a new rear triangle and extended seat post, I find I only use 5th and 6th most days and I've only once used the rack for a load, but the stability it adds to the folded package is evident based on observations of friends' bikes.
I enjoy having the range 6 gears gives me, but seriously considered changing to a 2 speed when my damaged rear triangle was replaced with a bright green one (rest being default black with light grey bar stem).
If I ever need to buy another it would probably be an S2-R for the stability on the train compared to bigger folders and the ease of rolling (by seatpost, or bars) on longer portages.