I have a Web2.0 client that is using it across the board (SQL Servers, middle tier servers and web servers). Nice stuff it seems, although I am just scratching the surface so far. This client has quite a few very powerful SQL boxes that aren't currently being taxed so I can't say much about perf hit.
Best,
Kevin G. Boles
SQL Server Consultant
SQL MVP 2007-2012
TheSQLGuru on googles mail service