The comments I've gotten (in person; none on the blog yet) on my previous post have ranged from "WHOA!" to "...what's Solaris?", via bemused rolling of the eyes. Those were from colleagues, university friends, and my long-suffering wife, respectively.
So I figure I should explain a little bit what Solaris is. It's a Unix operating system, one of many. That means that rather than being based (at some level) off the original DOS code, it's based off a different proto-operating system that is technically better-designed but a lot less user-friendly. Sun Microsystems develops it, although they've recently open-sourced the code (which means that anyone can change it now, and they don't have to buy the DVD from Sun to get it). It's only really as of the most recent release of Solaris -- version 10 -- that it runs well on PC hardware; previously, Solaris only really ran on Sun's own SPARC machines.
As a Unix variant, Solaris is a pretty strong one. It's scalable (which means that when you put it on bigger and better hardware, it can take advantage of all the extra processing power it has available), robust (which means it's difficult to crash), and secure (which means it's difficult to gain access to other people's files, or to pretend you're someone you're not). It also shares the advantages of Unix in general -- several of its core design decisions make it much easier to program for than Windows, it's more secure, and (at least right now) it's less vulnerable to worms and viruses.
Right now, Solaris' major competitor for the hearts and minds of the Unix community is Linux. Linux is better than Solaris at being user-friendly, better at integrating new features quickly, and less encumbered by silly executives' ideas of what makes a good operating system. Solaris is better at making big corporations happy with it, and at moving in lockstep with itself so that the whole package works with itself, and you don't have dumb problems where your keyboard driver's latest version doesn't work with the latest version of your motherboard driver, and there's no older version of your motherboard driver that also works with your mouse.... and so on.
So that's what Solaris is! Please feel free to tell me I'm wrong and why, if you also know what Solaris is. I'm sure I missed things.