Gave this a shot, but was not happy. It's a quiet back road, some nice bits, but the surface is really sub par. Rode it from Northampton end, and until you duck under the M1 I would say it's positively dangerous. It's really bumpy, to the point where it's very hard to control the bike. For the first time in years I had to stand the bike up mid corner and clamp it. Once you get past there it's an improvement.
Watch out for the large number of cyclists, and the cars that give them a VERY wide berth, to the point where they will be aiming at you, head on. A few very tight corners, heading south you wind up a fair way from the M1... Will try it S to N and report back :)
My preferred route home from work - some nice corners, a few that would be much better without the black lines or potholes, very rarely any police presence and light on traffic mostly :)
Spoghead