@Ray7: Android and Blackberry tablets seem to be popularly regarded as inferior iPad clones, at least so far.

 Does anyone actually have sales figures for Windows tablets? Are they much lower than sales of any other non-iPad tablets (or of Windows Phone 7 for that matter)?

This Windows slate, for example, seems to have an average rating of 4.5 stars on Amazon (from 77 ratings). Yeah, I know, it's a self-selecting fanboy niche and all that, but aren't Android tablets (and WP7) the same way? 

 I'm still not convinced that it would make sense to release a tablet version of WP7 this year. Windows 7 tablets are a stopgap until Windows 8 is ready, but a tablet based on WP7 wouldn't be any less of a stopgap; at least full PC tablets are differentiated from the iPad.

It's definitely risky though, since W8 won't be ready till mid '12, Microsoft is going to have a very rough next year-plus. The shareholders might not even let them go through with their plan before demanding drastic changes.