What Changes with XP?
There will be observable outcomes from your use of XP. If it's starting to work for you, there will improvements in collaboration and group dynamics. Your developers will have greater depth of respect for the company that has taken the risk to try XP, and they'll grow in relationships. The deepening of relationships is very important to both overall quality and results.
The standard of coding will improve as the superstars come down from on high to pair program with juniors. These juniors gain confidence, surprising seniors with creative solutions and wacky ideas. The dynamics of collaboration may form the team you've struggled to build.
On the technical side, the development team is exposed to new tools and advanced refactoring techniques. Commercially, your development team proves that they can delivernot just on time, but what the customer actually wants. Suddenly you have an edge over the traditionalists.