Using questions and answers to encapsulate knowledge is a great concept and SO does this really well. Besides, all developers already knows how to use the system. Content health tools help with making sure that knowledge stay current.

What I like most is that in a team non-ephemeral knowledge is shared almost automatically. Everyone asks questions, so by documenting these, everyone has access to this knowledge.

The best thing about SO for Teams is knowing that all the information you search is pertinent to your company. It is a great way to keep all the relevant information about standard operating procedures and the company's best practices in one place. The custom tags make searching for information even easier.