Value is the only thing that matters, are you bringing it or spending it? I'm not keen on the cost center solution when everyone gets "charged" for what they use to justify a central function but I do believe that it's important to keep the evaluation system up and running at all times. It's one thing to be the black box and be sure that everything is running smoothly, no one wants to be dependent but sure as heck when the things we count on aren't there or aren't working, it's hell for everyone.
I guess my question is that it's not important to brag, but it is important to continuously demonstrate the value you bring to the organization especially the decision-makers. Sure you need to send the quality metrics up your own chain of command, but you also need to make time to get to know the other functions that you are serving and use your team to stay in touch or on top of their needs and embed yourselves into their initial planning.
IT folks are often underestimated as problem solvers, and by forcing your team to be a regular collaborator and help the users see that they have more to offer you've done the best thing for everyone. Another way to look at this is to keep sharing ROA reports...or the returns that come form the assets you are managing. Do what you can to increase demand on the functions in your area that bring greater value to folks outside of your area. For example, if you are an IT manager, what systems or tools could people be using more to get greater efficieincy?
It's not enough to brag that you deliver, it's about helping and encouraging proper usage to create even greater beneifts for all parties. As you can tell, I'm more than a little passionate about this stuff. The only value to a black box is post mortem, after the accident. Don't make the mistake that bragging will avert outsourcing pressures, but if you create value that wasn't present, or if you contribute to another team's higher performance and they know it because your team was there holding their hands and guiding them along the way, THEN you'll be able to tabulate and demonstrate exactly what kind of a value ADD your function brings.
I've written more examples of this on my blog, encourage you to check it out.