Not that we have immediate plans to do so. This is more about moving forward. We build really large clusters and stack instances on them for many different apps. We have been doing this with SQL 2008 for two years now. Now we would like to start moving to building 2012. We know that we can easily run existing 2008 alongside new 2012 instances, but the big concern is if the business buys an app that will not run on 2012 (which in health care happens a lot; the vendors are slow and cautious when approving new platforms) and we are forced to install a new instance of SQL Server 2008. It would be cost prohibitive to build a new cluster just for the 2008 install, so the question becomes whether we pre-install five or six 2008 instances and turn them off for future expansion, or if we can go back and add them individually if really needed. I know this would NOT work on, say, 2005 and 2000, but I am wondering if MS has improved interoperability by this time.