Today, I had a simple question. Are the customizations schema (the exported .xml file) compatible across different update CRM 4.0 update rollups? Meaning, if I export a set of customizations (.xml) from a server that has UR2 (Update Rollup 2) installed, can I import that on a server having UR4? And how about the other way around?
Turns out that update rollup 2 and beyond are actually compatible with regards to customizations schema. Note that the only exception to this is UR1.
This KB article has lot more details about this: http://support.microsoft.com/kb/968176. Below is an excerpt from the KB article.