CRM 4 Update Rollup 5

As several others have announced, CRM 4 Update Rollup 5 has been released. There are a couple of notable points to make:

1. As with update rollups 3 and 4, the majority of the fixes have not been previously released as an individual hotfix. This is different from rollups 1 and 2, which were mostly a collection of previously released fixes. In general, I think that having fewer individually released fixes is a positive thing, but that has to be traded off against the frequency of rollups (currently about every 6 to 8 weeks), which is difficult to keep up with. Across our customers, we have deployments covering 5 different rollup levels, plus some customers on CRM 3, which needs a fair bit of management, especially with regard to schema compatibility
2. So, schema compatibility. Apparently, UR5 schemas cannot be imported into versions prior to UR2, but also, pre-UR2 schemas cannot be imported into UR5. I've got some investigation to do on this, but the most important factor for me is being able to use one development environment that can be used to export (and import if necessary) schemas to all rollup versions of CRM 4. Up to now I've rarely applied rollups to development environments, but it looks like from now on, UR2 will be a minimum requirement for a development environment. Either way, it makes life harder than it should be.