Let ATI lose some margin over not providing good Linux drivers, they'll come around pretty quick.
That's the beauty of a free market. Everyone has a choice.
You keep failing, huh?
ATI's parent company, AMD, was sputtering in it's death throes. They reorganized by splitting their chip design and fabrication companies in two and TAKING A HEFTY SUM from... get this... the goverment of Dubai.
I don't call government-subsidized anything "free market". It also calls into question one of your other points:
Let ATI lose some margin over not providing good Linux drivers, they'll come around pretty quick.
This has been happening for years. THey've NEVER provided decent drivers of Linux, and it's pretty obvious they have no plans to, having provided documentation to the Xorg developers to write their own damn drivers... that'll be here "any day now (tm)"
I guess it's like college. If all you're doing is partying, no need to be efficient.
I can see dismissing games (but even then, it's a difference in priorities, but not value) but you included "high end business apps". I will agree with you that FOSS apps can do about 99% of the things that proprietary, big ticket apps can. But if you've ever spent any time in a production environment in once of many industries, you'd see that the 1% it doesn't do is relevant to about 60% of work flow.
Case in point, the printing industry. GIMP couldn't handle CMYK for years and still can't handle LAB values for color. These are basic things in any printing shop slightly better than FedEx Office on training day. When you can toss out a single feature that rules out an entire industry, that's a glaring weakness, and ventures into the realm of "not partying". And believe me, with the overpriced apps that DO have these features, there's tons and tons of incentive to go with reliable, FOSS replacements. They simply don't exist.
I would say that Windows is also better for using the internet, since it's easier to find browser plugins for media
I'd say that installing VLC is about as easy on Windows as on Linux, so I think this is a tie, if not a slight advantage towards Linux. And unless you're referring to Windows 7, there's not even a comparison with NICs between Linux and Windows. XP and Vista don't find the intel ICH7 chipset which is used in almost every Intel board and has been out long enough that Vista could/should have installed it by default. Windows 7 even flawlessly detects and runs my Atheros9 wifi chipset but I've heard reports of people with pretty common hardware that didn't have a working NIC. NIC compat goes to Linux, hands down, IMO.
However, that is a limitation you face when running Linux, not Windows. Windows will work with pretty much anything you throw at it, by comparison. And it will work well unless the hardware is defective. As far as speed goes, I've never noticed much difference between the two.
I've got a scanner at work that runs fine with Windows XP and Linux, but not with Vista. The reason for this is that it's a cheap Taiwanese company that replaced it with a slightly upgraded model and dropped support. They never released a 64-bit driver for it and it was incompatible in 32-bit mode. Linux had a SANE plugin and it works just fine on 32 and 64 bit distros.
Windows having better support is about as wrong as saying that "Linux does..". There's a lot of Windows on a lot of architectures and some fail pretty badly, worst than Linux. The variable is why it fails.
Anybody who thinks that it's acceptible NOT to be choosy about hardware is someone you do NOT want building you a computer. They don't know what the hell they're doing - operating system is irrelevant.
As far as speed goes, I've never noticed much difference between the two.
I've got to agree here with a caveat. Most well-featured distros (Ubuntu, Suse) are about as slow as Windows 7. Sure, you can get a blazing fast Linux PC if you wanna use Dillo as your browser and run twm with a console log in instead of a greeter... and after you rebuild world to optimize for your architecture's instruction set and eliminate unwanted use flags.
If flexibility matters, Linux wins. If desktop usability matters, you can expect a decently bloated system that will, for 99% of it's existence, be loading useless crap into memory so it's there the second you want it regardless of what OS you use.
The DRM that is being built into Windows means that I cannot play media on Windows that I can by not using Windows.
Still more fail.

Windows, being the most used OS by home users, is the most popular target for open source software development. VLC's various codecs install on Windows with a few clicks, and open damn near any file that a standard Linux repo's will handle.
If not for Linux, I could not view them because they're not Region-1.
libdvdcss was written by the VLC people, works on Windows and ignores region.
And as far as browsing goes, it's Windows that has made it necessary for Google to warn people "This site may damage your computer!"
Actually, I think that's the result of dumb ass people being on the internet. Those kinds of stupid features are gradually making their way into Linux as more and more "average people" start using it (try rm -rf / in bash... Your Linux system, on most distros, no longer does as you tell it to and will actually ignore your command! How's that for control?)
It's not even a root/non-root thing. Windows UAC is actually pretty decent on Vista and 7 in terms of isolating system changes from the user. The problem, even with Linux users, is that they can be convinced they WANT to give malicious application X permission to run as root/admin.
No OS can eliminate PEBKAC errors.
Yep, the Windows "therapeutic reboot". Had to do it on servers in many places I've worked too, not just desktop systems.
In fairness, this is an apples-to-oranges thing. On Linux, there's no "third party vendors" to blame, unless you happen to be running an nVidia driver or something. Windows itself it actually pretty damn stable. Every crash or BSOD I've had has come as a result of a crappy driver or dying hardware, not Windows itself. With WIndows, you run the risk of being hosed by crappy third party support. On Linux, you run the risk of NO third party support. Which way would you prefer to be screwed is the question, since there's no "unscrewed" unless you feel like writing your own drivers which well... isn't a typical use case. And if you DO, would you please write a functional equivalent for fglrx on Linux using an Radeon HD 3200 chipset? kthx.
There certainly is a place for such integration, likely why I'm happy running KDE.
Operating system integration has it's place and my shorts have orange icing crumbs on them from my breakfast. Like your above statement, the two aren't related in the SLIGHTEST. Unless you intended to imply that KDE is somehow integrated, in which I'd respond with "Amarok 2 and Kopete Interfaces" and you'd be unable to return a cogent retort. And to your non-cogent reply, I'll reference the fact that KDE fails to detect composite capability in many composite-ready chipsets, refuses to activate desktop effects and proceeds to crash more often that hijacked planes on 9/11.
BTW, if you have any PowerPC Macs that seem to have been made obsolete by Apple's choice to go Wintel-hardware, Linux runs really well on those PowerPC.
Until it eats your bootloader and doesn't know what the fuck to do with New World partitions. And if by "runs really well" you mean "allows you to tinker for hours before getting tired and going to bed, to retry the same thing the next morning until you realize you're late for work and go, leaving the problem to be 'solved' later that evening with a reinstall you creatively justify to yourself."
I remember the last time I installed it on a SPARC, it was amazing how much that "antiquated" hardware could do.
Yeah, it plays those new, fancy YouTube videos pretty well... oh, wait... YouTube isn't new. And oh, shit, SPARC doesn't have a Flash plugin. But it's okay, you can install swfdec or Gnash.
Which is great if the ONLY Flash you'll be watching is YouTube. And the videos you watch don't need reliable sound.