continued from Firefox on Windows on ARM - Microsoft Says No
It's not precisely "running a browser in Classic" that matters for Windows on ARM. It's that running a browser in Classic is the only way that Microsoft has allowed us to get access to the APIs that a browser needs to deliver modern capabilities and performance in Classic AND Metro.
A browser running exclusively in Metro does not have the APIs necessary to compete with IE or any other modern browser.
On x86, Microsoft has given browser vendors the same privileges and APIs that IE uses. They have not done this on ARM.
That's why Windows Classic on ARM matters.
update: I've been asked by a couple of people on Twitter and email to elaborate. Let me give it a try.
On x86 Windows 8 PCs, there are three kinds of software programs.
First, there are Classic programs that are basically the same as they are Windows 7. Because of the rich win32 API available in Classic, these kinds of programs can be really powerful (or not,) but they can only operate in the Classic environment and cannot use any of the cool new features available in Metro and they cannot be run in Metro. In this category you can think of programs like Adobe Photoshop or Microsoft Word.
Second, there are Metro apps that are touch-focused, simpler, but have rich interactions between themselves and Metro and other Metro apps. These apps have access to some cool new Metro features but they live in a Metro sandbox and cannot use any of the more powerful features available from the Classic win32 environment -- APIs necessary for building a modern browser. In this category you can find apps like Angry Birds, Microsoft Stocks, or Hulu.
Third, there are Metro style desktop enabled browsers. These are programs that straddle Classic and Metro. They have access to the underlying win32 API like Classic programs and they also have access to the cool new features of Metro. They can have a classic front end and a Metro front end but under the covers they're calling into both the Classic and Metro APIs. In this category you have Internet Explorer 10, Firefox, and likely other browsers including Chrome and Opera.
Microsoft has made it clear that the third category won't exist on Windows for ARM (unless you're Microsoft) and that neither will the first category (unless you're Microsoft.) That means that IE on ARM has access to win32 APIs -- even when it's running in Metro mode, but no other Metro browser has that same access. Without that access, no other browser has a prayer of being competitive with IE.
Happy to answer any questions in comments.
update 2: I've also been asked why Windows on ARM matters. It's for tablets, after all, and that's just a tiny sliver of the larger PC universe.
That's true today, but it's not going to be true next year and the year after and the year after. ARM will be migrating to laptop PCs and all-in-one PCs very quickly. If you read Microsoft's blog posts about Windows on ARM, you'll see that they expect ARM PCs to cover the whole spectrum. ARM chips are already being used in servers. This is not a tablet-only concern.