nigeria is ok, just gotta be sensible about your stay there just as in any african country ie. food, malaria, transport, safety, security and atc... etc etc.... most of the time a bit of patience also sees you through!
i have had many happy uneventful stays in nigeria! not going to be a tourist there though very soon... couldnt find anything with lonely planet on nigeria....
i can vouch for almost all the big centres, except for lagos as i have not operated in and out of there!