I've been to Pisa for 4 nights and slept in one of the chain hotels NH, to be preciseCavalieri Hotel. The Hotel is not too low cost, it comes in fact 95 € per room double bed per night, obviously then this is the list price, often there are Offers or lastminute.
All in all, however, the hotel is valid starting from the accommodation up to the breakfast. The Hotel is in fact located in the station square, exactly in front of the main exit of Pisa station. There is nothing more convenient than arriving by train in a city and finding your hotel right away.
La breakfast è supercontinental. Empty and filled croissants, different types of bread, jams and Nutella, plus 3 different types of juice and centrifuged, bacon, eggs, cheese and cold cuts. Really great breakfast. Only flaw is that coffee or cappuccino can only be made from the machine.
Mine room was delightful although I have read some reviews on TripAdvisor not exactly reassuring. The Hotel has probably recently undergone a refurbishment of the rooms and many reviews are still old. However, I can assure you that my room was really nice. Furthermore, when you turn on the television or radio, the audio can also be heard in the bathroom :)