I ran across Linus back in 1991 and we could see he was on to something. Linux was pretty cool from the beginning. It just gets better and better and I've never had a Linux box fail due to the OS. I recall we had one Slackware machine with external DPT drives that was under load most of the time. The only reason we shut it down was to move it and at that time it had an uptime of about 3 years.
Right now I'm using xandros on one of my decktops and it's pretty cool.
The biggest problem with Linux, in my opinion, is that there is no one Linux, there are dozens of distributions. The average user doesn't want, and probably isn't qualified, to weigh the pros and cons of different distros. They want to install Linux period.
I know that some may view this as an advantage since different distros can be tailored to different needs. However, I don't think the average user would see it that way. If Linux weren't so fragmented, I think it could generate more momentum.