That may be true for Windows, bur he's also advocating using only MacOS and Linux/BSD. I think those issues are significantly less common, if not non-existent on those platforms...
That's true. As long as you use packages in your distrib format you don't have the problem on Linux. If you manually 'make install' from source it's harder to cleanly get rid of everything. But that's not recommended anyway.
Edit: there is some commercial software for Linux has custom installers which can result in windows-ish problems.
Have you ever/often bumped into problems with 'make install' leaving behind system crashing buts of code as time bombs when you've deleted the original app?
My personal experience is that if that sort of cruft accumulates in Linux, it happens at a slow enough rate that system upgrades fix the problem before it manifests.
Well a lot of mechanisms in Linux work by dropping files in a certain path (SysV init scripts, udev files, plugins). So leaving files around could have a little impact, such as runaway error messages, or a slight slowdown at bootup.
Then again, it's still much less than in Windows. And it's more transparent, resolving the problem is generally a matter of removing the file, instead of going into the registry jungle "trying random stuff from the internet until it works".
