My main gripe is the price (I am poor by european standards). For example going from Paris to Napoli only by train is currently above 300 euros whereas you can find a flight for 40 euros. I am ready to pay around 100 euros for that. Recently there was sleeper car train from Paris to Milano which was affordable but the company did not last alas. I am personally ready to pay more in order to avoid a flight, I don't even care about the time it takes, I like being on trains. Sleeper cars are even better. The only thing is the price.