Been using the toast  tool for a while after having investigated to varying degrees the following:
- GNU Stow
- ESP Package Manager
- Smart Package Manager
My own usage is under Debian (and a bit of Gentoo). Some use cases include:
- Want to use a more up-to-date version of something (and/or would like to patch), but would like to be able to cleanly remove traces / disable / enable
- Want to use something on a host which lacks that something, but don't have administrative privileges -- and even if I did, don't want to impact other users' environments
Please share stories!
 The best introduction to toast I've encountered so far is the article:
Installing and tracking software updates with toast
If interested, I recommend looking at the toast manual after reading the article.