Take a look at this link from MSDN. It may answer your question in part.
In the platform support section:
Windows Internet Explorer 9
Important Windows Internet Explorer 9
is only supported if you have
installed Visual Studio 2010 Service
Pack 1 The following scenarios are
supported if you have installed Visual
Studio 2010 Service Pack 1:
You can create an action recording or
coded UI test with Internet Explorer 7
or Internet Explorer 8 and play this
back using Internet Explorer 9.
You can create an action recording
using Internet Explorer 9 running in
compatibility mode and play this back
with Internet Explorer 7, Internet
Explorer 8 or Internet Explorer 9.
You can create a coded UI test from an
action recording or by recording
actions using Internet Explorer 9
running in compatibility mode. You can
run this test with Internet Explorer
7, Internet Explorer 8 or Internet
Explorer 9.
Important You cannot create an action
recording using the standard mode for
Internet Explorer 9 because the new
features and controls for Internet
Explorer 9 are not currently
supported.