You never know when a subway station is all of a sudden and completely out of nowhere going to get flooded. This was Sunday afternoon at the N/R 57th Street stop which I seem to use a lot. The best thing about this stop is that the trains come very regularly and there are usually no long waits for trains even if the station floods from time to time.
The transit system in Manhattan is totally unpredictable, but I imagine it runs pretty well compared to other cities. I prefer the bus for the ride and the weird people who you see on the bus, but the subway is way faster and much cheaper than taxi cabs which are totally outrageous. I was running late the other day and a cab from 57th Street to the World Trade Center was $19. Serves me right for being late I suppose.