Glossy, highly reflective-looking UIs are currently quite popular. While there are many ways you can suggest a reflective surface using gradients and hilights, some of the simpler effects are often the best. Here is a simple approach that uses two rectangles placed on top of eachother inside a grid, which gives a nice reflective appearance.
Xaml Code (Jul 2006 CTP)
<Page xmlns="
http://schemas.microsoft.com/winfx/2006/xaml/presentation
"
xmlns:sys="clr-namespace:System;assembly=mscorlib"
xmlns:x="
http://schemas.microsoft.com/winfx/2006/xaml
" Background="#785429" >
<Grid Width="200" Height="70">
<Rectangle Stroke="#FFe1e1e1" RadiusX="10" RadiusY="10"
HorizontalAlignment="Stretch" VerticalAlignment="Stretch"
Width="Auto" Height="Auto" x:Name="Rectangle">
<Rectangle.BitmapEffect>
<DropShadowBitmapEffect ShadowDepth="2"/>
</Rectangle.BitmapEffect>
<Rectangle.Fill>
<LinearGradientBrush StartPoint="0,0" EndPoint="0,1">
<GradientStop Color="#FFF9F9F9" Offset="0"/>
<GradientStop Color="#FFd9d9d9" Offset="1"/>
</LinearGradientBrush>
</Rectangle.Fill>
</Rectangle>
<Rectangle Stroke="{x:Null}" Margin="3,14,3,3"
RadiusX="14" RadiusY="10" HorizontalAlignment="Stretch"
VerticalAlignment="Stretch" Width="Auto" Height="Auto">
<Rectangle.Fill>
<LinearGradientBrush StartPoint="0,0" EndPoint="0,1">
<GradientStop Color="#FFE8E8E8" Offset="0"/>
<GradientStop Color="#FFE4E4E4" Offset="0.2"/>
<GradientStop Color="#FFbdbdbd" Offset="1"/>
</LinearGradientBrush>
</Rectangle.Fill>
<Rectangle.BitmapEffect>
<BlurBitmapEffect Radius="1" KernelType="Box"/>
</Rectangle.BitmapEffect>
</Rectangle>
</Grid>
</Page>