I know it is a bit late, but in case anyone comes here via search - here is a solution to set hover style for rows using MouseOver / Out CSOM client-events, hopefully it will be useful:

<igtbl:UltraWebGrid ID="UltraWebGrid1" runat="server" DataSourceID="SqlDataSource1" Height="200px" Width="325px">
    <DisplayLayout>
        <ClientSideEvents MouseOverHandler="Over" MouseOutHandler="Out"/>
    </DisplayLayout>
</igtbl:UltraWebGrid>


    <script type="text/javascript" language="javascript">
   
    function Over(gridNane, cellID, objectType)
    {       
        var cell = igtbl_getCellById(cellID);
        setRowBackColor(cell.Row, "red");        
    }
   
    function Out(gridNane, cellID, objectType)
    {       
        var cell = igtbl_getCellById(cellID);
        setRowBackColor(cell.Row, "white");    
    }
   
    function setRowBackColor(row, color)
    {
        var cells = row.getCellElements();
       
        for (var i = 0; i < cells.length; i++)
        {
            cells[i].style.backgroundColor = color;       
        }  
    }
   
    </script>