I want to second this. Living in flats sounds cute for most of the people who never lived in ones that are being built with cheap materials and thin walls. It's all nice and dandy until a sill neighbour moves in and then you've got nowhere to hide.
Living in a poorly built flat is a bad experience, sure, but there are well built flats out there, where you can only hear your neighbors if they're actually being loud--really not that big a problem.