I looked at going 2 years ago, but it was hard because of the time limit of the Angolan visa at the time. You could +apparently+ get a visa in Yaounde, or a Dutch guy said you could get one on the Cameroon border (on coast) for €70.
Despite wanting to do it when in Kribi, I still had to go to Yaounde for the Gabon visa, so went down from there to Gabon.
My main feeling was it was going to be the same jungle as southern Cameroon and Gabon. And it was raining heavily every day and I couldn't find much info about roads and bridges and was worried about having to come back to Cameroon with no multiple entry visa.
Also it's a pretty horrible dictatorship....
Given more time I would have gone, but I haven't heard anything that makes me hugely regret not going etc.
Go and let us know! ;-)