Please refer to the attached sample project. The ResizeColumnsProportionally.gif illustrates the correct behavior of columns resizing. However, if you make a certain column with fixed size, the columns resizing is not proportional any more. The ColumnsWidthNOTAdjustedProportionally.gif demonstrates better the wrong behavior.

Workaround:  handle the SizeChanged event and adjust the columns' width property programmatically in order to obtain the desired widths.

To reproduce:
 this.radGridView1.SummaryRowsBottom.Insert(0, summaryRowItem2);
 this.radGridView1.SummaryRowsBottom.Move(2, 0);

Workaround:
Remove all items and add them back with a spesific order. 

How to reproduce: check the attached project and video

The new mode should allow copying of single cells even when having the SelectionMode set to FullRowSelect. The attached project features a possible workaround.

By default, when I am expanding a group and start sorting, the expanded group doesn't collapse. However, if you use a group comparer, all groups will always collapse, when you click a header cell to sort.

To reproduce:
- Add 7-8 columns to the grid.
- Set the AutoSizeColumnsMode to Fill
- Set the MaxWidth/MaxWidth of the last two columns.
- Resize the first column.
- Sometimes the size of the other columns is randomly increased/decreased.

This new API will be useful for implementing custom sorting scenarios when you need to have custom sorting only for a single column.

A similar API is available for the filtering functionality (MasterTemplate.DataView.FilterEvaluate)

To reproduce: we have a RadPageView with two grids on two pages. The first grid has a ColumnGroupsViewDefinition applied. When you open the Property Builder and try to hide some of the columns, the error occurs.

Workaround: make the changes programamtically at run time.

To reproduce: please refer to the attached gif file and sample project

Workaround: set the AutoSizeRows property to false

To reproduce: run the project, select the grid and press Tab. You will notice a message box for the first grid which won't be shown for the second in the popup.

When I add summary rows to my radgridview. something strange is happening.
I demonstrate it to you in two pictures. please take a look at attachments

The selection mode should be as in Windows Explorer - when Control is pressed, one should be able to move the current row with the up/down arrow keys and when Space is pressed, the current row should be selected/deselected. 

This implementation can be used for the time being:
  public partial class Form1 : RadForm
    {
        protected override void OnLoad(EventArgs e)
        {
            base.OnLoad(e);

            AddGridSimpleUnbound();
            radGridView1.MultiSelect = true;

            BaseGridBehavior gridBehavior = radGridView1.GridBehavior as BaseGridBehavior;
            gridBehavior.UnregisterBehavior(typeof(GridViewDataRowInfo));
            gridBehavior.RegisterBehavior(typeof(GridViewDataRowInfo), new MyRowBehavior());

            radGridView1.GridViewElement.Navigator = new MyNavigator();
        }

        class MyNavigator : BaseGridNavigator
        {
            protected override bool DoMultiSelect(GridViewRowInfo oldRow, GridViewColumn oldColumn, GridViewRowInfo row, GridViewColumn column)
            {
                if (!this.IsShiftButtonPressed && this.IsControlButtonPressed && !this.IsMouseSelection)
                {
                    return true;
                }

                return base.DoMultiSelect(oldRow, oldColumn, row, column);
            }
        }

        class MyRowBehavior : GridDataRowBehavior
        {
            bool kbdSelection = false;
            public override bool ProcessKeyPress(KeyPressEventArgs keys)
            {
                if (kbdSelection)
                {
                    kbdSelection = false;
                    return true;
                }
                return base.ProcessKeyPress(keys);
            }
            public override bool ProcessKey(KeyEventArgs keys)
            {
                if (keys.KeyCode == Keys.Space && this.GridControl.MultiSelect && keys.Control)
                {
                    this.GridControl.CurrentRow.IsSelected ^= true;
                    kbdSelection = true;
                    return false;
                }
                else
                {
                    return base.ProcessKey(keys);
                }
            }
        }
}

Similar property is already available in the property grid and tree view exporters.

To reproduce:

Sub New()        
    InitializeComponent() 
    Dim items As New List(Of WorkOrder)
    For index = 1 To 56
        items.Add(New WorkOrder(index, "Item" & index, 0))
    Next
    Dim rand As New Random
    For index = 57 To 500
        items.Add(New WorkOrder(index, "Item" & index, rand.Next(1, 56)))
    Next

    Me.RadGridView1.Relations.AddSelfReference(Me.RadGridView1.MasterTemplate, "Id", "ParentId")
    Me.RadGridView1.DataSource = items
    Me.RadGridView1.AutoSizeColumnsMode = Telerik.WinControls.UI.GridViewAutoSizeColumnsMode.Fill
    Me.RadGridView1.EnablePaging = True
    Me.RadGridView1.PageSize = 20
End Sub

Public Class WorkOrder
    Private _id As Integer
    Private _name As String
    Private _parentId As Integer
    
    Public Sub New(id As Integer, name As String, parentId As Integer)
        Me._id = id
        Me._name = name
        Me._parentId = parentId
    End Sub

    Public Property Id() As String
            Get
                Return _id
            End Get
            Set(ByVal value As String)
                _id = value
            End Set
        End Property
    
    Public Property Name() As String
            Get
                Return _name
            End Get
            Set(ByVal value As String)
                _name = value
            End Set
        End Property

    Public Property ParentID() As Integer
            Get
                Return _parentId
            End Get
            Set(ByVal value As Integer)
                _parentId = value
            End Set
        End Property
End Class

Workaround: use standard hierarchy: http://docs.telerik.com/devtools/winforms/gridview/hierarchical-grid/hierarchy-of-one-to-many-relations

Example : if we have 5 rows in the grid and if we copy 10 rows from excel and paste in first row, only first 5 records gets pasted and remaining 5 would be ignored.