In an excellent post Eileen Brown discusses Service Level Agreements. There are a couple of points I'd add onto to end of this nice article.
First, you need to have SLAs before you can improve them. For many organisations, "it just works" is the expected level of service, whereas what's delivered is what's delivered and any gaps are just the way it is. Organisations should have SLAs for all critical infrastructure.
Second, you can't improve what you are not measuring. While I'm not hung up on measuring by dollar value, in order to improve any service you have to have some baseline and a method of detecting changes to that baseline. Thus you need to measure constantly. MOM and SCE help you do this.
This leads to the third point - why isn't MOM part of every EA/SA contract in some way? I was doing a bit of consulting for a large public body who planned to have 22 DCs spread out across hundreds of square miles. The plan was to monitor partly by driving around - MOM was "too expensive". A quick back of the envelope calculation reckoned you could get the licenses and hardware for £10k including basic installation. Seems cheap to me for an EA costing hundreds of thousands of pounds each year. Include it please!
Finally, in order to manage service you need processes in place. These include ITIL and Microsoft's excellent MOF. I don't know about you, but I find process a hard concept to sell. The sales guys don't get any commission for selling ITIL/MOF - they prefer to shift what pays them. As Drucker observed: People respond as they are measured. And, I suppose, by how they are rewarded. Inside organisations, process means more work - and IT folks are already stretched. One good way to help here might be to include mandatory MOF or ITIL training for all IT staff as part of large corporate roll outs. How about making IT Pro focused MCTs have ITIL certification in order to be an MCT, and have operational processes discussed in every Microsoft course?