Here's a question to think about:
Are Microsoft causing the PC market to decline by producing an OS that is less PC-orientated (as many on this thread suppose), or is Microsoft making their OS less PC-orientated because they can tell that the PC market is in decline?
Possibly both. It's hard to tell if their hedging their bets or trying to tap new customers (probably both though you don't want to ruin your cash cow and then fail in the market you hedged to).
I strongly feel that with some small UI changes MS could cater to both the desktop and tablet market.