Plaster and timber flooring isn't so bad. Brick is also better than concrete. More rigid materials tend to transmit sound better.
Once I lived on the bottom apartment in a two storey apartment block. The floor boards were a nightmare and eventually we had to move. Upstairs footsteps across the floor were loud enough to wake us up, and I don't just mean squeaky boards, but just the thumping knocking sound resonation. Sometimes I could make out the words being said in their conversations. Never again.