Pros
1 ) Most valuable learning opportunities
2) Methodologies
3) Self improvement and also work for the deprived
4) Coaching
Cons
1) like some one already mentioned, your efforts always get noticed only if you are favorites of the Boss.
2) No scope of progress, you have to be a boss boaster to get into next level and need not work at all only prove yourselves once in your tenure.
3) Target given to people not responsible and person responsible is asked not to do work.