I know VS11/SL5 aren't supported yet. I just wanted to post this so it can be fixed before they are. As soon as a RadOutlookBar is added to a XAML page Intellisense stops working. Delete it and Intellisense works again. Tried this on a couple machines. To test it out start VS11, create a SL5 project and add the code below to the XAML page.
After you add the code type in '<' and you'll see there is no Intellisense. Then remove the code below and type '<' and you'll see it working again.
<telerik:RadOutlookBar HorizontalAlignment="Stretch" x:Name="LeftBar" Width="250" MaxWidth="300">
<telerik:RadOutlookBarItem Header="Open Projects" Content="Open Projects Group Content" />