Hi Derek, Kevin and How,
In the soon-to-be-arriving IC614 release there are many enhancements to the ruler capabilities, such as the ability to draw and then remove specific rulers. Since this is an in-built capability, it will behave similarly to the existing ruler in the way that you can see the ruler and tick marks and sizes while it is being drawn (which you don't see if you are using the enterLine enter function). The ruler function will also have built in "smarts" so that itcan guess if you are measuring from edge to edge, corner to corner etc. based on ruler direction and initial points. It will use, I believe, the gravity aperture as the search window for the point and can be made to "snap" to point types (e.g. center, edge, vertex).
Hopefully the new capabilities will address many, if not all, of the concerns that layout designers have about rulers.