Of course the trains are crowded at rush hour - that's why it's called rush hour. However, it is nowhere near unbearable, and certainly not any worse, in my experience, than NYC. But there's one huge advantage over NYC - you don't have to worry about pickpockets, so you can relax while riding the train and take a nap, read a book, or play some games on your phone (which is what most of the commuters do).