There are a ton of new features in visual Studio 2010 but it can be difficult deciding exactly which edition of Visual Studio 2010 to purchase for your team members. This presentation attempts to identify some of the high-level scenarios and recommends which Visual Studio editions to purchase. There is also a "scenario combinations" slide that starts attempting to put together the most common.
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More information about this topic available here: http://www.edsquared.com/2010/04/02/Which+Edition+Of+Visual+Studio+2010+Do+I+Buy.aspx