Positive aspects which make me put 4/5 and not 3 are:
-Perfectly located flat. You cannot find better in terms of localisation in Chania. Soooo close to the sea, close from the old town, close from everything that you'd need, 15min by foot from the main bus station that will lead you everywhere that you'd need to go. You walk at the end of the street (less than one min) and you find the sea + a wonderful viewpoint. You have a cool beach nearby too!
-The host was really kind and helpful, she answered every questions that we had and she replied fast.
-The aunt upstairs is also kind and helpful, she will tell you everything that you'd need to know.
-There's every cooking tools that you'd need. There's an oven etc.
Negative aspects according to us:
-It is badly soundproofed. You hear everything from everywhere. We had to wear earplugs every nights and it wasn't enough. There's no sounds at night, only in the morning... so if you want to wake up early every days it won't be a problem for you.
-it has a washing machine but it's all written in german;
-No TV (although it is written on the description)
-No doors between the bedrooms (although it is written on the description)
Overall it's 4/5 because of the positive aspects i described above, it is worth for you to rent that flat.