Given your environment, I'd stay with Windows. No, I'm not a Windows fan, but I recognize that software development, subsidized software development that is, is much more heavily tilted toward where the market is. Since Windows used to be 90% of the market, it's not hard to tell where vendors would be spending their resources. That's not to say that open source wont eventually have what you're looking for, but it would probably be a longer wait. Also, :-) by then your requirements would have changed and you will want something that the opensource crowd will be running to catch up to.
On the other hand, if you come from a teletype / dialup background like me, your wants would be drastically fewer and simpler. Eventually your TV/DVD/Game console will probably be doing all sorts of computer kinda stuff and you will fondly remember how you could waste several hours figuring out how to put italics into your emails. :-)