I actually went back to check when it was implemented, and I found out that Alpha 4 introduced the sections system, wich should improve the pathfinding of colonists, but I still run frequently in kinds of situations where pawns don't take the best way.
Example:
Guy wants to eat a meal, there are two simple meals availible on the map. One is in 15 tiles distance, but guy had to walk around a mountain to get it, so it's like 200 tiles away. The other one is 30 tiles away with a clear path. My people always take the first one in this situation.