Yes, I was watching Mix10 live and I looked at the developer tools before they were announced. The link
Windows Phone for Developers | Windows Phone: Developer Home was where the 6.5 tools were and morphed to WP7 early. They are exactly what was expected from all the previous hints. There is nothing really new but it does make cross-platform development possible which is probably a good thing. The problem for me is that the platform is aimed squarely at implementing lightweight media applications which don't interest me at all.
XNA is purely for games, and maybe a few other specialist applications. It provides a Calc/Draw loop for repetitive execution of timed game code. XNA does not stand alone but is a structure within .NET for writing game loops. XNA apps have the same (limited) access to the platform facilities as Silverlight apps.
Silverlight is effectively the replacement for the Compact Framework but using a subset of WPF instead of Windows Forms. In itself not too bad but the problem is that Silverlight applications run in a security sandbox. Fair enough as they are meant to be downloaded from the "cloud". The problem is that they lock the programmer out of interacting with the platform apart from the APIs that are made available in .NET. I've looked at Silverlight 3 and 4 beta and they are very restrictive. For example you don't have access to the full device file system, only to a private folder which is isolated from other apps. You won't be able to get at the Registry. You can't have a local database like SQLite. You can't interact with other applications. You won't be able to P/Invoke the native APIs where some facility you want is only avalable there, in fact, unlike WM6 they probably won't be documented in WP7. Also the actual WP7 platform is limited in its' user interaction as there is no stylus and the touch screens will be capacitive, which are not high precision devices unlike resistive ones. So even though Silverlight does support ink for mouse or stylus equipped PC or tablet platforms, on WP7 you will not be able to implement precision user interaction like capturing handwriting nor implement a CAD style or drawing application nor write an accurate photo retouching app because of the hardware limitations. The entire orientation is towards web based media and games applications.
I can't believe that Microsoft doesn't have an on-going strategy for enterprise applications like interfacing custom hardware, warehouse data collection or order taking. Whatever that strategy is, assuming they are not just going to abandon that market sector, I can't see it being based on WP7.
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