I always found the Contingency Planner pretty useful, but only in 3-5 player games when you're more likely to see Special Events earlier and have more events in the deck to find and take advantage of (also because of the nature of the role, it taking a relatively lower proportion of the actions in the game is an advantage). It is of course a luck dependent role, based on what events are in the game and how soon they come out, but they're generally useful. I don't think it's one of the best roles, but I think it's pretty decent.
Basic general use I'd say is, be a little more liberal with special event use over the game, since the CP can pick it up later. When you don't have anything especially good to do with an action, grab whatever special event seems most likely to be useful in the upcoming turns.