This is great, but you can't actually configure virtual machines unless you're one of the "select members of the community". So, if you sign up today, on the three month trial, you can't just configure a linux machine and test it.
If you even manage to get to the correct place, which is a Silverlight powered management console - when HTML5 / AJAX would do.
Lots of bloat and lots of cruft and no actual functionality.
I should clarify that it's Internet Explorer _on Metro_ that won't run Silverlight (as far as is known). And, in consequence, ARM tablets won't either (because there will be no desktop mode, just Metro).
On the other hand, the new XAML-based API will be a somewhat easy upgrade path from Silverlight app to native app.