Windows chief Steven Sinofsky at Microsoft’s Build devel­oper con­fer­ence as reported by Daniel Robinson, V3.co.uk:

We’re not going to port the installed base of x86 appli­ca­tions to ARM. They don’t take advan­tage of the things that make ARM a great architecture.

But Microsoft has announced that Windows 8 will run on ARM. So there is only one con­clu­sion. Take it away John Gruber:

I had been read­ing state­ments like this as mean­ing that they wouldn’t be doing Rosetta-style emu­la­tion of x86 soft­ware on ARM [...], but that devel­op­ers would be able to recom­pile tra­di­tional Windows apps for ARM. Now I’m think­ing what they mean is more pro­found: that on ARM, Metro will be the only Windows interface.

Metro is actu­ally a well thought out user inter­face (UI). Jensen Harris, Director of Program Management for the Windows User Experience Team, intro­duced the Metro UI in great detail dur­ing Build. The com­plete lack of chrome lead­ing to an ele­gant, min­i­mal­ist user expe­ri­ence cen­tered around con­tent is what impresses me. iOS in com­par­i­son feels heavy. Again here’s Gruber:

So I hereby amend my pun­ditry. Windows 8 with the full Windows desk­top will never be an iPad rival. But a ver­sion of Windows 8 with noth­ing but Metro looks like an excel­lent design for an iPad rival.

The Metro UI cer­tainly seems to be a wor­thy rival to iOS on the iPad. But a bril­liant UI alone isn’t going to get you places. Take a look at what many con­sider a superb mobile OS: Palm’s webOS. It’s going nowhere. And there are many rea­sons for that.

Tight inte­gra­tion between hard­ware and the OS wasn’t there. HP makes good enough note­books and desk­tops, but when it comes to tablets, good enough isn’t good enough. It’s clear HP couldn’t get beyond good enough with the TouchPad.

A robust army of great devel­op­ers with effi­cient tools to cre­ate amaz­ing apps, weren’t there. A place to securely and eas­ily pur­chase those apps in addi­tion to a huge mul­ti­me­dia library was absent, too. For all of these rea­sons and more webOS despite it being a solid mobile OS didn’t make it.

Sure, Metro looks nice, but Microsoft will need a flaw­less exe­cu­tion on the entire tablet expe­ri­ence to not only com­pete with the iPad but to beat it.

Update: Well, there goes Gruber’s the­ory. Joanna Stern put up a video show­ing an ARM-based tablet run­ning Windows 8 with both Metro and the tra­di­tional desk­top.