I don't think I've ever really experienced with a rootkit, I mean on the other PC, we most definitely were infected, just it was long time ago when I didn't have a clue what a rootkit is. I don't think I ever had one on my laptop though.
Just once on my old PC, When I was to say a "novice" user back then, I remember when I first installed my first AV, AVG Free it found a rootkit I remember its red bold words exactly.
But since then no infections what so ever.