Given the amount of violence that accompanied it, and the fact that it was instrumental to the political and economic exploitation of African peoples, I don't see why "infrastructure" is particularly positive. It's a "positive" if we assume that the African peoples who did not already have roads or whatever actually really wanted them or that they had some particular benefits, but I don't really see any reason to look at that as a big bonus. Infrastructure isn't just some universal good, it benefitted certain peoples more than others, and in Africa the real beneficiaries of railways and harbors were Europeans.

I am not a historian, but what is interesting to me is that three countries - Botswana, the Gambia, and Senegal ( as of 1989) were the three notable functioning multi-party states. Most other African countries were ruled by a one-party state or a military government.

I think that colonialism made it hard for Africa to develop. The African 'big man' in many ways, just replaced the colonial governor, as a person who handed out patronage to a specific ethnic group to keep control and extract resources without developing the country. Additionally, I think the imperialism's association with the West and capitalism in the minds of many African ruling elites created a tendency to follow the centrally planned, import substitution model (either Soviet or Fabian Socialist) which turned out to create stagnation not growth (hydroelectric plants that were expensive but inefficient, steel plants that produced expensive, low quality steel when cheaper, better steel could have imported, etc.). Ivory Coast's post-independence ruler is one of the few who embraced a more American style, free market model (with mixed results). An ineffective leader in Africa could always turn to be being anti-Western and still, at least early on, tap into lingering grievances from colonialism.

However, after independence (1960s), African country were positive about the future. If multiparty states could have been established in these states instead of one party states or military governments (something the fact that Africans were 'states not nation-states', the dynamics of the Cold War, and unfortunate cycles of rain and drought, and how dependent African economies are on a fluctuating commodity prices made really unlikely), my uneducated guess is that Africa would have had a much different path despite the obstacles created by colonialism.

Source: Meredith, Fate of Africa (2011). I am on page 460 right now. I'll return to this comment when I am done with the book. http://www.amazon.com/The-Fate-Africa-Continent-Independence/dp/1610390717