The fastest way to encourage adoption is to get Silverlight on as many platforms as possible -- Windows Mobile, iPhone, Mac (all flavors), Linux, Android, Windows Embedded, MCML, and so forth. The more platforms, the better.

Implement all WPF binding scenarios.

MOST WANTED:

1. Binding of non-framework elements. (Now you cannot bind properties of Behaviors and Triggers)

2. Binding of style setter

3. Ancestor relative source binding

4. x:Type x:Static ...

We really tired of Silverlight data binding hacks =(

In addition to being able to print and offer basic reporting, Line of Business apps need to easily be able to output to Excel, PDF, XPS. If I show a data grid with Sales Data to a VP at my company, they are going to want that data in Excel in one click.

Add Reporting Controls Support

Provide some sort of local SQL database with Silverlight OOB (so it could be used without stepping out of the sandbox) for a standalone OOB app

PersianCalendar is a class which was added to System.Globalization namespace from .NET 2.0. But it is not included in Silverlight now.

Silverlight has showcased how it performs and its fabulous flexibility and performance in interface development, together with all the added sugar of the .Net platform.

I am suggesting to make it the lead development technology for Windows 8.

To make some use for the webcam/mic support announced for Silverlight 4, some video/audio encoders should be built in (for example Windows Media or h264/AAC). Also there should be built in support for streaming audio/video to either a Windows Media server or to IIS using live smooth streaming.

Out of browser is fine (SL 4 Beta), but it is also needed in browser so that "3rd party" html content can be incorporated into a Silverlight application (actually a show-stopper for me).

.Net 4 includes PLINQ and TPL. Silverlight 4 should, too. I want to use these in my app and run it on both .Net 4 and Silverlight 4.

Something equal or better than the new Flash Text Engine in Flashplayer 10

Silverlight is about giving the users a first class UX.

I don't think that it's first class to let the user enter a document name each time the download a document.

We have to use ASPX for download until this usability bug is fixed.

Please also make the dialog title writable.

Thanks

Right now the bitmap APi is primitive and needs more functionality as well as performance enhancements. We also need more functionality on the GPU, especially the shaders and 3D abilities in WPF. This would give game developers some serious power instead of what we have now.

Improve the Silverlight WCF stack by providing support for wsHttpBinding and wsDualHttpBinding

I know that what we really need is a FlowDocument control, with Select+Copy support, but until that arrives, it would be very useful to be able to select and copy text from TextBlock controls.

Weather or not this is possible, should be set as an Attribute on the element (SelectAndCopy="True"), - Thereby enabling texblocks to act like labels and/or HTML-like paragraphs ...

Silverlight 4 prints by rasterizing the content to bitmap and sending this bitmap to printer. This has many unpleasant side effects - print jobs are huge, especially on high DPI printers and long documents, printing to PDF or XPS is essentially useless, because the output contains just bitmaps, etc.
Please, implement proper vector printing like WPF, Flash, GDI, Windows Forms etc.