PostgreSQL capacity ?

Hi, I have been checking out the PostgreSQl project and I should say I'm
surprised the incredible work developers and others have done. Now I
would like to know if there is some document which can light me to
evalute the capacity of PostgreSQL.

I got a friend who should start an information system project for the
place he works. They really do not have much money and would like to
evaluate all posibilities. I commeted about PostgreSQL and he's very
interested to know some information of performance or capacity to
compare against MS SQL Server and others.

I will really appreciate all your inputs about this, thanks,