correct layout in the base classes and what your derived types have copied over when their images were built before. This leads to inconsistencies or even crashes, so these images all need to be recreated. I didn't want to scare people away by getting too technical :), but if you're interested in more details, I highly recommend watching the Channel 9 video with Mani Ramaswamy and Peter Sollich. He provides some very nice explanations that demonstrate when and why generated assembly becomes stale and needed to be recreated, and how MDIL solves this problem. Re: Windows Phone 8: Compile in the Cloud compiling to MDIL has the same degree of "inherent obfuscation" as using native code. When you look at the output you'll realize that it generates assembly that is dependent on the CPU architecture, with some place holder tokens and specific instructions the "linker" knows how to treat. However, do not forget that what you as a developer upload to the Phone Store still is IL, and if your application supports 7.x those users will get the same IL assemblies like before - so no, I wouldn't say it eliminates the need for obfuscation at the moment, if you're sensitive about your code. The concept of MDIL is compelling and there have been hints that it is thought about how or if it can be brought over to other platforms to make them benefit from it too. However, at the moment there are no official announcements on this (that