We have recently completed a major survey into the deployment styles used in MDM implementations. My colleague Dave Waddington has recently posted a summary of the results here. As can be seen, MDM projects are turning out to be quite meaty in size, but encouragingly the sucess rates were higher than I was expecting.
There were several quite interesting results that came out, and we will be doing further research into this area. The full report can be purchased from our website.