
Linux only has a small percentage of the computing market, however Microsoft already considers it a major competition as the open source OS steals the hearts of many users. Following the hard numbers though, Microsoft also increases its market share on both server and desktop space with time. The only logical explanation is that Linux steals quite a market share from the traditional UNIX providers (SCO, Sun, SGI, HP, IBM). But only Sun seems to truly be in a real Linux trouble, as it is the one with a resistance to Linux integration to its full product range.
Linux and the free BSDs are very similar - each have their own strengths and weaknesses and based on pure merit... I (my opinion) personally prefer FreeBSD, BSD developed alot of what UNIX is today. Sun and IBM furthered UNIX greatly, each in their own right. Both operating systems are nothing short of amazing (Solaris 9 and AIX 5.2.) Yet both vendors see the inevitable strength (irresistable force) of open - source software.
Two points if I may...
#1 Linux is not better, it is just free...
#2 CISC processors are now just CISC / RISC decoders that run really fast... and its inherent raw speed is overcoming its inefficiency. So Linux on Intel is cheap, cheap, cheap... that is why it is doing so well...
You think if Solaris x86 was free and open for development (under GPL) 5 years ago this would even be a debate, everyone would be using Solaris, same goes for AIX... But no one saw Linux coming and now no one can stop it because it has too much momentum, it is a buzz word like NT was 5 years ago (and XP is today.)
I think you will notice that RedHat benefits more than the others, they have started selling it for huge amounts of money. A sure sign for business idiots that it is "enterprise ready". Which means RedHat sooner or later will become synonomous with Linux... like Xerox and copies (which I hope won't happen, but it probably will.)
Solaris and AIX lack nothing, they are at the moment both superior to Linux (imo), but the Linux kernel is just improving over time and will surpass them, it is just a matter of time. The fact is binary compatability, price, and "buzz-word" power make this OS unstoppable. For better or for worse. Of course pure engineering genius and powerful OS's will fall everytime to the current industry buzzwords... just how life is, its the class "prez" in the IT high school =)