Microsoft could have solved a lot of problems by releasing the Courier instead of taking two years and releasing the WinRT units. It would have solved:
Time to market.
Clarity on legacy Windows apps -- there's no mistaking it's not going to run old Windows apps.
Differentiation from the rest of the tablets on the market. Courier was unique.
Even if Courier was developed on a modified W7 kernel (oh the horror!) they could have done the same kernel swap they did with WP7 to WP8.
As for WinRT and opening up the desktop for other apps that are ported to ARM... As much as I'd like to believe it would help the assumption is that the apps were written well enough to run on ARM and provide reasonable performance. Developers love to lean on Moore's Law.... Also keep in mind Microsoft's guidance on writing Windows Store Apps with RT's lack of performance in mind.
While the SurfaceRT and it's RT companions are interesting IMO they are too limiting and confusing for most consumers especially for their price. I was in Best Buy just last weekend check out the W8 devices as I'm looking for a laptop or tablet for my daughter. Time and time again I had to correct misinformation that people were given by the Microsoft reps that were there. Even they don't have a clue on what this thing WinRT is. I finally went over to talk to the Microsoft reps so I could verify for myself what they were saying. When I asked about the discrepancies I was hearing one of them shoved a Lenovo Yoga in my face. Yeah because the Yoga (Windows Pro) can do everything that makes WinRT ok too.
For the record my nits with what they were saying or misleading on SurfaceRT were:
The 32GB Surface had plenty of storage on it. (they never disclosed how much of it was free space nor did they mention cloud storage as an option.)
You can use your existing printer with SurfaceRT. (Only if it's supported... we all know the history here with this little gem.)
You can use Maps to lookup directions (you sure can but only if network location can pinpoint you; no GPS on the SurfaceRT)
OneNote could record video & audio (not with OfficeRT)
OneNote supports handwriting recognition (not like Officex86; OfficeRT doesn't support handwriting directly on the page. You have to write via the ink input method and use your finger or capacitive stylus. Oh and yes it sucks.)
When I cornered them on these issues they smirked and acquiesced.
And last but not least their explanation about not being able to run legacy apps was not hitting the radar of the folks I spoke with about the RT devices. Many were stunned that they couldn't run Quicken or any of their old software on it. I know the reps were trying to make this point clear but it just wasn't sinking in. And that my friend is why RT is going to be a stinker -- a product you have to explain isn't a product that will sell itself.