What is the best way to slide a panel in WPF?

I have a fairly simple UserControl that I have made (pardon my Xaml I am just learning WPF) and I want to slide the off the screen. To do so I am animating a translate transform (I also tried making the Panel the child of a canvas and animating the X position with the same results), but the panel moves very jerkily, even on a fairly fast new computer. What is the best way to slide in and out (preferably with KeySplines so that it moves with inertia) without getting the jerkyness. I only have 8 buttons on the panel, so I didn't think it would be too much of a problem.

Here is the Xaml I am using, it runs fine in Kaxaml, but it is very jerky and slow (as well as being jerkly and slow when run compiled in a WPF app).

  <UserControl xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Width="1002" Height="578">
     <UserControl.Resources>            
        <Style TargetType="Button">
           <Setter Property="Control.Padding" Value="4"/>
           <Setter Property="Control.Margin" Value="10"/>
           <Setter Property="Control.Template">
              <Setter.Value>
                 <ControlTemplate TargetType="Button">
                    <Grid Name="backgroundGrid" Width="210" Height="210" Background="#00FFFFFF">
                       <Grid.BitmapEffect>
                          <BitmapEffectGroup>
                             <DropShadowBitmapEffect x:Name="buttonDropShadow" ShadowDepth="2"/>
                             <OuterGlowBitmapEffect x:Name="buttonGlow" GlowColor="#A0FEDF00" GlowSize="0"/>
                          </BitmapEffectGroup>
                       </Grid.BitmapEffect>
                       <Border x:Name="background" Margin="1,1,1,1" CornerRadius="15">
                          <Border.Background>
                             <Linea