I did Ekok to Mamfe about a month ago on my little scooter.
Basically, as soon as you cross the road to Cameroon the road turns to dirt/mud/rocks. They are in the process of building a new road from but for the moment you still have to twist and turn through the jungle on the rough road. You'll crisscross over the new road constantly as you do. As long as it's not too wet, the road itself isn't TOO bad. Actually, I had a lot of fun on it. About 10km before Mamfe you'll get to parts of the road that are near completetion and have an easy finish. After Mamfe, it depends which way you're going. I went south to Kumba, the road starts really bad, has a stretch in the middle that's paved, and then end badly again. The roads between major cities in Camerooon are all very good though.