As noted in the previous post, I upgraded to Win 7 the other day. The upgrade from 32bit to 64 required a clean install so every program had to be reinstalled.
Evernote definitely wins the award for easiest install. Reason is that all your Evernote files are in sync between your computer and their cloud. Therefore, simple matter of just installing the new Evernote on the new clean drive and sucking down all your data from the cloud, organized just as it used to be.
Making use of Microsoft's new Mesh tool when switching computers or doing a clean install is also worthy of a mention. Any folders you have synced up to the cloud with Mesh can of course be dropped back down onto your computer. Different than Evernote is that you have to re-select the location of the folders on your computer which requires an extra step (I'm not suggesting Mesh should work like Evernote--different functionality).
Of course if one is using a Mac, none of these issues are relevant because upgrade paths have not required a clean install for a long time. Upgrading to a new Mac from an old one is just a matter of connecting the two with a cable and zipping everything from one computer to the other, programs as well as files.