When the Expression_Dark theme is applied to the RadPropertyGrid, selecting an item is hard to read, as the item's foreground is white and the selection state is in a similar color.

To work this around, use the following Style:

<Style TargetType="telerik:PropertyGridField">
    <Style.Triggers>
        <Trigger Property="IsSelected" Value="True">
            <Setter Property="Foreground" Value="Black"/>
        </Trigger>
    </Style.Triggers>
</Style>

 Add selected inactive state for PropertyGrid Field.

When a RadPropertyGrid instance is placed inside a RadBusyIndicator, the StyleManager cannot apply the styles correctly and it causes an InvalidOperationException at runtime.

Workaround: Use the NoXaml version of the assemblies with the needed themes.

An non edit mode is enabled in the control when the EditMode is set to Single. In this case, only one field can enter edit mode and the rest are read only. 

Currently, there is no API that allows you to customize the content (that shows the property value) of the read only fields.

Add an API that allows you to customize the read only content. Similar to the EditorTemplate of the PropertyDefinition.

Currently, the control allows you to search only for fields that have been expanded already. If a parent field was never expanded, the search won't look for its children.

Allow searching in not expanded fields.

If you have a data validation, and there is an invalid field with the red border around it, if you hide this field via the filtering feature or the collapsing its group, the validation red border (and the tooltip) disappears.

To resolve this, you will need to update the ErrorTemplate of the input field (the TextBox). You can do this in the FieldLoaded event handler.

Behind the scene we need to update any changes made in the property grid, in a SQL Server database, too. With our current implementation we fire a database request if a property is edited in the property grid. This is fine if only one entity has been selected. If more than one entity has been selected (ProperytSetMode “Intersection”) a database request is fired for each entity if a property is edited. This is not very performant for us.
We need an event like “EditEnded” to figure out when the PropertySetViewModel has updated all ViewModels. Then we are able to updated the necessary changes in the database in a single call. 

The item status is set to Declined as it is already logged in our system: https://feedback.telerik.com/Project/143/Feedback/Details/202982-propertygrid-selectedpropertydefinitions-are-not-cleared-when-radpropertygrid-it.