By adding the new reflection API's to the older platforms you create a unified experience which is less confusing then the current one, especially for Portable Libraries.
It also makes it easier to write platform specific code that is not yet portable and link the files.
Also, in this way the direction for reflection is clear and people can get used to the new API's.

use as in Windows application

When Ria Services are autogenerated, there are quite a lot of useful comments with TODO suggestions. As a newbie to Silverlight and Ria Services, it would be helpful if there were also links to sites that provide more information on how to do what is suggested needs to be done.

Provide a native .Net class library to replace WININET.dll. Currently, retrieving HttpOnly cookies can only be made via WININET.dll which additionally has a dependency on Internet Explorer 8 and above. Retrieving the FedAuth Cookie is a common operation for Claims-based SharePoint development, therefore, this functionality should be built directly into the .Net Framework class libraries.

Managed .net support for: IStorage (MSG-Files), DragDrop(complete incl. MSG-Files), Clipboard(complete!), Sound, Ribbons, Floating/Dockable Toolbars with customizable customization dialog, Docking, Tabbed MDI, TAPI, CAPI, MAPI, Aero-Design (gradients, Colors...) and so on, of course implemented in libs also beginning up from 3.5 to 4.0!!

The datatypes Byte, Decimal, Double, Integer, Long, Short, and Single should implement a new interface INumber, where common functionality like addition, substraction, multiplication and division is exposed.

This will allow the easy implementation of classes that needs that functionality like typed matrix classes:

public class Matrix<T>
where T: INumber
{
Matrix<T> Add(T scalar);
Matrix<T> Add(Matrix<T> matrix);
...
}

The current approach forces the developer to implement the matrix class multiple times.

Introduce an attribute (let's say StrictEnumAttribute), which will restrict assigning non-explicitly defined values to enums. So currently the following is possible:

internal enum Features
{
FirstFeature, SecondFeature
}

public void DoSomething(ref Features argFeature)
{
argFeature = (Feature)5;
}

I'd like by marking the Feature enum with StrictEnumAttribuet that conversion to fail during compilation.

Please add a class for external windows like http://www.vbforums.com/showthread.php?t=644071&highlight=Window
This would be very useful if it Contained ALL Windows Api Functions related to windows.

Make .net libaries re-usable in silverlight with no change. At this time we have to use file linking and other tricks. It will be nice to make it re-usable by directly refering .net projects in silverlight.

When I'm writing a plugin DLL for a Windows service that DLL often has to call a WCF service application.

I can easily reference that DLL's <appSettings> section, but I haven't found any means to alter the executing code's config file source for the WCF service. (That data would have to be copied into the host service's config, which is not ideal)

Ideally, there should be a way to have the executing assembly to be able to use either the host's config file (Host.exe.config), or the plugin's (Plugin.dll.config)

In actual version of .NET there's one class to create word documents, but it's so confused and slow. I think that creation of new and better version of this class will beneficial for programmers.

Listeners of UI events such as click, selected index changed, text changed, etc should be capable of discerning if the particular event was raised as a result of a hardware interrupt such as a keyboard or mouse input as opposed to resulting from a coded change of property (EG: comboBox.SelectedIndex = -1).

This information could be stored in the EventArgs,
EG:
private void Text1_TextChanged(object sender, EventArgs args)
{
var originalSender = args.MessageInterupt.Sender as Control;
if(originalSender == null || "text1" != originalSender.Name){
MsgBox.Show("text changed by code");
return;
}
MsgBox.Show("text changed by user");
}

To use ProtectedData.Protect to encrypt a SecureString instance, the instance first needs to be converted to a byte array which defeats the purpose of using the SecureString class.

Please add an overload to Protect that accepts a SecureString instance instead of a byte array. A new Unprotect method will also need to be added that returns a SecureString.

It would be great if the StringBuilder class had a AppendLineFormat, so you don't have to escape newline/carriage return, call multiple methods or use String.Format for archieving the same.

Sounds like a simple and quick change to implement

The TaskCompletionSource<T> class should have a non-generic base class that would implement the methods that are currently in TaskCompletionSource<T> and which don't operate on the result type.

Specifically these are: SetCanceled, SetException, TrySetCanceled, and TrySetException.

This would allow for canceling/failing a diverse collection of TaskCompletionSource objects without needing to know what the result type should have been.