annie21d said:

1. If merging is done on a column containing checkboxes, a checkbox is displayed in the middle of the group of merged cells. Is it possible to have it displayed on the first row of the group instead?

You can align the checkbox to the top:

        private void ultraGrid1_InitializeLayout(object sender, Infragistics.Win.UltraWinGrid.InitializeLayoutEventArgs e)
        {
            CheckEditor checkEditor = new CheckEditor();
            checkEditor.CheckAlign = ContentAlignment.TopCenter;
            e.Layout.Bands[0].Columns["Boolean 1"].Editor = checkEditor;
            e.Layout.Bands[0].Columns["Boolean 2"].Editor = checkEditor;
        }

annie21d said:

2. If merging is done on a column containing buttons, the buttons are not visible at all. We did set the property "ButtonDisplayStyle" to "always" but the buttons are showing only when we click on the cell. How can we ensure the visibility of a button if its column is merged?

Since the buttons don't merge, anyway, you can simply set the MergedCellStyle on the column to Never.