To be fair, at least with Windows, if you do a reinstall I've always found that it never runs quite like it used to. I've sometimes had to deal with some weird quirks afterwards. A friend of mine who kept switching between Google Android and open-sourve Android on his phone said the same thing. Every time he reinstalled Google Android, it simply wouldn't run as well as it did beforehand.
It's like taking a plumbing pipe out and putting it back in. Or taking apart a car engine and putting it back together. It never quite fits together the way it used to anymore.