Having worked daily in Lion, Mountain Lion, Mavericks and now Yosemite I can say that for myself, I do mind upgrading.Although I know this is kind of unrelated, I dont mind upgrading to newer versions of OS X because not all the changes are intrusive like they are on Windows *cough* WIndows 8 *cough*. I just don't want to upgrade because I will have to upgrade the rest of my apps which will be a pain in the rear
Lion killed the ability to reduce the size of Finder windows past a specific minimum, which is way too large for my setup. Both ML and Mavericks have a SMB/CIFS bug that prevents me from staying connected to the server for more than 24 hours and will instantly kill InDesign when the connection is lost.
Mavericks came up with that dumbass tagging ball crap instead of real labels. I've had to resort to the feature in XtraFinder. And Yosemite, although it fixed the SMB/CIFS bug, is no great improvement on either of the last three versions.
El Capitan locks down system files, preventing you from making any modifications and starting with Lion Apple hid the user Library folder.
So, all the way around for me I'm good with Snow Leopard.