Vista is already far less crash-happy and far more secure against malware and viruses (as long as you don't disable UAC like the whiners do) than any previous version of Windows. Now that the Windows 7 RC is socking it to Vista, I imagine we will see a fairly quick adoption of it by both XP and Vista users. When the majority of Windows PCs are running Windows 7, I'm guessing we'll see a significant reduction in the amount of infected systems.
Personally, I don't have much respect for any company whose sole marketing strategy is nothing but mere mudslinging. If your product isn't good enough to sell without badmouthing the competition every chance you get, then I have no interest whatsoever in buying it. Even if it was superior, I wouldn't buy it based on principle alone. Granted, Microsoft has had its share of questionable marketing tactics, but the Mac vs. PC ads from Apple are nothing but a collection of facts taken out of context and twisted into non-real-world scenarios.
The fact of the matter is, Windows is great, and so is Mac OS X. Choice is a good thing to have, and those are two great choices, depending on what you're looking for in a computer. Just stop the mudslinging already. These stupid commericals are making you all look like 6-year-olds bickering over whose toys are better. Promote your products based on how good they are, not how bad you think your competitors' products are.