We are in a booking.com property in France. It's kind of like a hotel room with a kitchen. Entry via key safe. It's very central for sightseeing and nice enough but has quite a few issues:
Dirty plates and utensils in kitchen. Either looks like they didn't come out of dishwasher clean or covered in dust as not used.
Sheets for sofa bed (for kids) - bottom sheet did not smell freshly laundered and had stains 
Rugs look like they need a good clean
No soap in bathroom dispenser, just in shower.
The sheets issue is blurgh, the rest are minor. It was late when I discovered the sheets so we put extra pillowcases over the offending area.
Will hopefully speak to owners today, I left messages last night with booking.com and was told they would be passed on. I'm so shit at complaining. Should I ask for money back or discount or what??? I don't speak French.