I generally avoid hills so I found some of this a bit of a struggle, especially as it was quite muddy and very overgrown in parts. However, I was rewarded by amazing views and a lovely downhill stretch into Marlow. I will be doing this again, but intend cutting off the part that goes under and by the side of the M40 as it just spoils an otherwise tranquil ride in the countryside. There are other tracks (bridleways) that will allow this close to The Harvester.
Although the on-road parts are reasonably quiet, I would not recommend this for young children, particularly Winchbottom Lane which is narrow in parts and has its fair share of inconsiderate drivers. Fine for older children though.