I'm new to Settlers of Catan, and I quickly learned the importance of having a source of Brick and Lumber at the start of the game. And some googling showed that others agree ... and others disagree.
Whatever you value most at the start ... brick, wood, grain, ore, (ok, not wool so much), diversity of resources, diversity of numbers, access to ports, etc., you can find a blog post confirming your belief.
What is much harder to find is actual data. Has there been any significant study of competitive games and/or computer simulations that give substantial support to a particular initial placement strategy?