I think that the new Metro-style apps look fantastic. I haven't gone into the details about WinRT at a technical level yet, because there are few details available.
A number of people have asked, "what about phone and Xbox?" It's a good question, and right now, there are no answers. Microsoft isn't saying if WP7 (or WP8) is going to merge with Windows 8, or if it will remain separate.
WinForms, Silverlight, and WPF are still supported by VS11. I am surprised Microsoft isn't saying that WinForms devs are officially obsolete and need to stick to VS2010 or earlier, but there is still time for that to end. If you are writing an application now, it will still work with Windows 8. If you want to write an application that takes advantage of the touch interface functionality really well, and works great on a tablet (and possibly a phone or game console), Metro/WinRT will be the way to go. I see the big problem for legacy (non-Metro/WinRT) devs is that the experience of using these apps is currently quite poor; hopefully, Microsoft can improve that between now and the final version. For the time being, it feels very clunky to go to a Windows 7-style desktop that lacks much of its functionality (like a "Start" menu).
For developers who want to write Metro/WinRT applications, the transition is going to be rough, unless you have already been working in Silverlight or WPF. Even if you have used WPF, that will give you the XAML and application model concepts but not the UI paradigms. The UI model that Metro/WinRT uses is straight from WP7. In the demo apps, there is no easy way to exit. I assume that Microsoft uses a WP7-like tombstoning/multithreading model, because the only way to break out of them is CTRL+ESC. Likewise, in WP7 apps, there is no "legal" (as in, "will get past the App Hub testing process") way to deliberately exit the app. Don't like it? Neither do I, and neither do a lot of other developers. It makes sense for a phone and probably a tablet but not a desktop OS.
I realize that it is early in the development cycle of Windows 8 -- the release isn't even mature enough to be called a beta, and there is roughly a year before it hits gold status by most estimates. Microsoft has been slammed by a ton of analysts, industry observers, and reporters about its habit of announcing things like this in public well in advance of the actual release. Those folks are only seeing the PR side of things; for us developers, who are the lifeblood of Microsoft's ability to maintain or grow Microsoft's market share, we needed to see this now. The Metro/WinRT apps are a major change, and Microsoft needs us on board now so the company can launch with a full slate of quality titles. Think "new game console" style launch, not a traditional "new OS" launch. The problem is that unless Microsoft makes the experience of using legacy apps a lot better, Windows 8 will be a very unpleasant experience overall. And the new Metro-style apps are not mapping well to the keyboard/mouse; for instance, things that on a touch screen require a simple finger swipe now require the user to hunt down a scroll bar and use it. Metro works great on my WP7 phone and I love it there, but just as the Windows UI was a mess when translated to Windows CE and Windows Mobile, the Metro UI is a wreck on a desktop PC.At this point (in other words, if nothing changes on these items between now and final release), I think this is a good time to decide if you can transition your applications to Web apps. Metro/WinRT is lousy for apps that do complex work. Meanwhile, IE10 is very invasive throughout Windows 8. While I often dislike Web apps, I think that for sophisticated tasks, they are better than Metro/WinRT from what I've seen, and the legacy app experience is so bad that not many developers will want to use it if they can avoid it, and new apps will feel very dated.
Regardless of what shakes out in the final project, it is clear that Microsoft is signaling that sophisticated desktop applications are a relative rarity, Web apps are much more common, and for the things that use local resources, users prefer simple apps on the phone/tablet level of complexity, not applications like we see now. I think Microsoft's strategy may backfire, as developers choose to write Web apps (possibly with non-Microsoft technologies) instead of trying to make their applications work in the very unique, non-backwards-compatible Metro/WinRT style, or having their applications using the clunky legacy desktop.
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Justin James is the Lead Architect for Conigent.