We were staying at the flat for an 11-day stay with our two children of 6 and 10. We really very much enjoyed our stay with Diogo and Filippa. Yes, you could see and hear the trains but that was clear enough from the pictures and did not bother us. The bedrooms are in the back and the noise did not disturb our sleep (nor that of our children). The flat was certainly clean enough -- that was the one point I was a bit worried about when reading some of the reviews but that was not needed. The location is also great -- just two minutes from metro and Santa Appolonia. We also liked the terrace with its view on the Tejo and the station. There were some minor things that could have improved our stay (eg more towels in the kitchen and more storage space -- especially when traveling with children and staying for a longer time). The lamps shown in the bedroom with the two beds are no longer there -- it would be better if the plastic sticking out of the wall would be removed.
Price/quality this is a very good place also for families and I would be happy to go back there.