Inter-city travel in Côte d'Ivoire is usually more comfortable than travel in neighbouring African countries. The roads are generally in good condition and the bus service is relatively modern. The down side is the very frequent military check-points which add hours to a trip. Though the stops are a hassle, Ivoirian soldiers tend to be pretty professional and don't hassle non-French western travellers. Soldiers in Ghana for example are much more likely to demand a bribe than in Côte d'Ivoire. Most western governments recommend that their citizens steer clear of Côte d'Ivoire. This should be taken particularly seriously by people travelling on French passports. An Ivoirian soldier's attitude towards you will change very quickly when you explain that you are not French.
UTB - Union de Transports de Bouake offers frequent busses to most destinations of interest. Their bus stations are widely known in the cities and are semi closed compounds so travel is not a hastle.
Travel in Abidjan is the best when you have your own vehicle to travel around. The roads are fairly good for the region, but traffic rules are flouted routinely, especially by taxis. There is no lane discipline and traffic lights are merely suggestions. Traffic jams get bad at rush hour and some selfish drivers make things worse through illegal and often reckless maneuvers. The police response to this is laughable, as they are unable to chase/punish the worst offenders and shake down people who aren't doing anything wrong.
Taxis are a great and easy way to get around in Abidjan. Just look for an orange coloured car and flag it down. Fares are very affordable: US $2-4 depending on the length of the journey. Always negotiate before you get in the taxi -- don't use the meter as you'll almost always pay more.