I am still excited about moving to an distributed source control management system. I think there are a lot of benefits that would come along with it, however, there are also a number of obvious costs that I haven't been paying attention to.
Our current scm, perforce, is used to store both code and our content. My original goal was to have a single SCM system for both. By keeping code and content in the same system, I thought, we could more easily manage releasing code and content together. However, our content publishing system allows us to abstract the deployment of content to a certain extent using publishing "packages" (ie p4 labels) and should allow us to run separate systems and still meet our release management requirements. So, while I would like to have one system to manage perhaps, it is not such a hard requirement.
My biggest concern in moving is that we have a large number of developers and, due to our content management system using perforce as its data store, a large number of non-developer users. It will take time and training to move the hundred or so people to a new scm. The amount of money spent moving people needs to be weighed against the efficiencies gained via git (or mercurial). Some of these costs can be diminished by preserving perforce as our content repository and only moving our code to git (or mercurial). At the end of the day, moving to a new system needs to provide more benefit than the cost and time sucked up by moving. Right now I am beginning to be skeptical that that is the case and I am beginning to think that there are more pressing problems for us to tackle, such as continuous deployments.