Do you think that appreciating a team member's good work in front of the team is a good or a bad practice?

It is great...........if you do it to encourage the employee and NOT compare her/him against a non-performer!

Appreciating someone's good work in front of others would go either way, but this should be done to an extent where the person who is being appreciated is motivated and other team members are also encouraged to follow and work more efficiently and effectively. 

Note - Criticism should always be done privately.