Package management, kernel modifications, the ability to know whether or not your machine is back-doored, among other things. The ability to run an OS that will actually run on other hardware. The fact that it's open source also has a lot of indirect value to many of us as well.
I was with you until you implied Linux can't be back-doored. There's nothing about Linux that makes it immune to rootkits or backdoors despite what the hype would have you believe. Remember, Apple used to say the same thing about Macs, but you don't hear a lot of that rhetoric nowadays.
