Here's an alternative that works well for readability if you have the Binding in the middle of the string or multiple bindings:
<TextBlock>
<Run Text="Temperature is "/>
<Run Text="{Binding CelsiusTemp}"/>
<Run Text="°C"/>
</TextBlock>
<!-- displays: 0°C (32°F)-->
<TextBlock>
<Run Text="{Binding CelsiusTemp}"/>
<Run Text="°C"/>
<Run Text=" ("/>
<Run Text="{Binding Fahrenheit}"/>
<Run Text="°F)"/>
</TextBlock>