If you write equations, create design tables, use DriveWorksXpress or have any other reason to view your dimensions while in an assembly or part file then you’ll need to know where to find the setting after upgrading to SolidWorks 2010.
Among the user interface enhancements that SolidWorks made in 2010 is the ability to quickly toggle the dimension visibility. In SolidWorks 2009 and older the option was a system level setting that could be toggled on or off.

Starting in SolidWorks 2010 the setting is no longer within the System Options menu!

This is due to the Show Dimensions option being moved to have its visibility capable of being toggled like a user would toggle visibility for planes, sketches etc. You can access the Dimension Names visibility from the View pull down menu.

You can also access it from the Heads-up View Toolbar.

The Show Dimensions setting is also now controlled and saved on a per-document basis instead of being a setting which applies to all documents.