The secret is to make the upgrade path seamless - if I have to navigate an obstacle course of library dependencies, config file format incompatibilities, system conflicts or complicated data migration issues, I'll just skip the whole affair.

All too often devs get blinders on and don't realize that most people don't have their domain knowledge and therefore it's not quite so easy for them to see the forest for the giant stacked trees that are lying across the path.

If you can't avoid that morass, the new version better offer something so compelling you can't possibly skip it.