Well in Lithuania we say that spiders brings luck to your house and you shouldn't kill them
Of course except when their population gets out of control you start to feel out-dominated in your own home
I live in a flat too and had a problems with cockroaches in the kitchen year and a half ago.
There were lots of them, especially at night
My own efforts to kill them all was kind of poor, since I only managed to decrease their population instead of killing them all. I remember I even got a nightmares to dream that dozens of cockroaches are crawling on my bed
One day I lost my nerve and called a pest control service for help.
They quickly did a job for good. From that time I never saw any of those awfull looking bugs