Look at every OS alternative to Windows that has failed in the past. The vast majority fail for not having enough software alternatives available to match what is available for windows. Linux has been around for quite a while now, but main stream software is still hard to come by.
Application installs in Linux are difficult, and often require additional software that must be downloaded in one of several cryptic ways prior to installing the application you want to use. None of it is as simple as a application install in Windows.
Linux's usage model should be the automobile, but in actually they opt for the spaceshuttle.
The Mac OS is probably the directon Linux should be going in. Though I wish OS manufacturers could give us a way to have it both ways.
I also think the Linux community at large wouldn't want to beat Microsoft, they need something to be the counter culture to.
"My sense of purpose is gone! I have no idea who I AM!" "Oh, my God... You've.. You've turned him into a DEMOCRAT!" -- Doonesbury