There are many things to investigate if you are worried about SSIS performance or would like to optimise package execution.  One of the things to take a look at is the SSIS Pipeline events in performance monitor.  There is a counter called Buffers Spooled which, quite simply, indicates the number of buffers which are spooled to disk.  This is worth monitoring if you are concerned there is memory pressure.  Ash also talks about performance tuning in great detail so I advise you to check out his blog at http://sqljunkies.com/WebLog/ashvinis

On a slightly different note; a new whitepaper has recently been published on sqlskills.com titled The Database Administrator’s Guide to the SQL Server Database Engine .NET Common Language Runtime Environment.  The whitepaper can be viewed here: http://www.sqlskills.com/resources/Whitepapers/SQL Server DBA Guide to SQLCLR.htm - I'm always interested to read about the other cool features in Yukon.