I don't know why the downvotes.. Very high rents for rather low quality (by the european standards). Long and unpredictable commutes, frequent problems on the overcrowded lines. Serious pollution: today the subway/metro was free of charge for everyone in order to encourage people to use the (already crowded) public transportation instead of cars to reduce the thick smog which accumulated over the city.

http://www.leparisien.fr/info-paris-ile-de-france-oise/trans...