We have a policy of reviewing changes before commiting them (not really extreme programming..). Only if review says ok, the author can commit changes.
A team server also can "review" it by compiling and running tests.
It would be nice if team server supported the following scenario: to send a change to server first for "review", and if results look good, ask for a human review. (perhaps electornically - sometimes there is a need that someone from a geografically different location must review the changes. we have special scripts to generate html "diffs" and place them to a web server) Then, if human review is also ok, instruct the server to commit the change to repository.