
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.
I myself am quite fascinated by the other architectures asides from x86. I guess I like Linux well enough, but I'm more of a Unix enthusiast than a Linux one. Lately I'd come to the same sort of conclusion about Linux, with respect to the longevity of the big iron Unix lineup.
MS may have 95%+ of the market but they aren't the threat to Unix diversity or Unix itself. Windows is windows, I couldn't care less, but Linux is, to take the usual star trek theme, like the borg. Slowly but surely it's absorbing the rest of the market and taking over whereever the other Unices are moved out, be that SGI shops moving to x86 render farms or Alpha clusters for (more) x86 ones. The Unix vendors have no weapon against it that differentiates themselves for long. I don't really think that by and large companies suddenly say 'let's move to Linux' from another Unix line, but when their flagbearer trips up (SGI, maybe Sun) or buries them (good old HP) it's a good enough alternative, and not a business decision I can blame them for, considering. But in so far as I can see it's a trend from dedicated systems that excel (for their time) to generalised systems that will just do, the watermark of x86 I'd add.
To place this admitted ramble in context, I personally have x86, SPARC, Alpha, PA-RISC, and SGI/MIPS computers (and if you count PDA's, ARM too). Running Linux on each of these widely different architechtures is near exactly the same. For me personally that is entirely besides the point - you might as well just get an old pentium for all their actual performance but that's not of course why I bought them. The fun part is in exploring what these systems individually do well, and they can only do that with their "own" Unix running on them. The death of these systems heralds the death of elegant solutions to computing problems, but that's not all Linux's fault (and at that, for being too good), but it's part of it.
I do not dislike Linux, just what it's going to take part in doing to make the not-windows world as homogeneous as windows itself is.