What are the implications of compiling packages from source? For example, what if doing sudo apt-get upgrade upgrades a dependency of the manually-installed package? How would using a package from the PPA differ in this respect?
Another implication is that it cannot be automatically updated by the package management system (How would you update it manually to keep the settings of the package if it's an application)?
I want to ensure reasonably compatibility and stability while using some programs that need to be compiled from source (aren't available in the default repos or third-party repos). Are there ways to make this possible? What about a package from the PPA?