Every week, more and more bits of malware seem to be making their way past commercial anti-virus, firewall anti-virus, and ISP anti-virus software. New patches and downloads abound, and I've still re-imaged 3 computers in the last 2 weeks due to massive infestations. This is to say nothing of the home computers about which my users are complaining (I feel like getting one of those ThinkGeek T-shirts that tells people, "No, I won't fix your computer.")
I'm well aware that if Linux or Mac had greater marketshare, then they would be far more vulnerable to malware attacks. That being said, right now, none of the computers in my house (four of them, all Mac or Ubuntu) have had even a blip of malware. My students who have switched over to Linux? No problems. Teachers with Macs at home? No worries. Schools with Macs in them? Not a single issue. You don't notice people reimaging their MacBooks because of a trojan.
There are plenty of reasons to use Windows PCs. Games, proprietary Windows-only software, generally low acquisition costs; the usual arguments apply. However, as I have to turn more of my attention to ensuring that my Windows PCs stay malware free and I watch my *nix computers hum along happily, I'm struggling to see a good reason to stick with the Windows platform.
Right now, I have a significant investment in a Windows back office. In just over a year, though, all of that equipment will go off lease and I'll be refreshing a lot of Windows servers and PCs. Will I replace them with Windows computers? I just don't know that it's a smart idea.
We don't play games, we're moving our curriculum away from teaching specific applications and focusing on computing concepts, and I'm tired of intrusive, moderately effective anti-malware software. Even less intrusive software like Clamwin can only do so much to help clueless users, even if it is less of a pain on a daily basis (and it's free).
I don't know that I can rationalize Macs for the tech refresh. We've relied on thin clients for too long now, acquisition costs are too high, and I simply don't need high end kit at this level, no matter how cool OS X server might be. That leaves me with some other non-Mac flavor of Linux. Solaris is looking mighty nice as a virtualization platform and LTSP/Kiwi/Edubuntu and the like just might be mature enough to meet my needs at that point.
I have too many options open to me, though, to keep dealing with the hassles of Windows. I'm not making any decisions just yet; I have plenty of time to give this serious consideration. Who knows, maybe Microsoft's Morro will be really awesome. I'm not holding my breath and I'm not going to stay wedded to Windows when the time comes just because I finally have my AD tweaked just the way I like it.