Well I arrived in Pointe Noire this afternoon. Took the direct road SW from the logging community/crossroads of Mila Mila (S3.71613 E12.44991), which is next stop south after Kibangou (and like the road, not on Michelin map). Took me longer than I thought at 6 hours (but not riding hard as I bent the torsion arm on my rear end a couple of days before, hitting the exit of a bridge too hard. Straightened it, but I want it to stay that way!).
125 miles, and a very interesting ride. Medium-rough, over very interesting terrain/scenery, certainly at the Mila Mila end. Up and down quite a lot, a lot of dust and stones sticking up - certainly not nicely-graded piste on the whole - but the logging lorries are doing it. Think a 2WD would struggle not to damage sump etc. But no mud, although I could see evidence that there had been a lot of slurry about, so probably I was lucky with the weather.
I asked a lot of people on the way down, and this seemed to get the vote over going via Dolisie, though not unanimously! And I dare say easier than going to Brazzaville - I was told it's not good now.
Came down main route via Ndende etc, first, as if towards Dolisie. Worst sections (mud) were from border to Kibangou, but not all the way, and not bad, just a few mud holes and pretty slippery when it rains (and it DID!). Think it all depends on the weather at the time more than anyone's past experiences.