I rode it from Dieppe to Forges-les-Eaux, on my way to meet fboab and Fidgetbuzz after PBP '11.
No problem with a road-bike; I used my Pompino, loaded with camping gear, probably 28mm tyres.
It's a great route - although what with ferry timings (the 11:30pm Newhaven ferry dumped us in Dieppe at 3am!) the first 20km or so was in the dark. The whole section I rode on was tarmac, smooth, and wide - wide enough for two separated lanes at the road crossings, which are really well done, I thought.