I’ve posted here before about using expressions to modify how a label component offsets. In the upcoming 2009 release one of my favorite new features is the Drawing Scale Conversion in expressions.
The Drawing Scale Conversion is the scale of the drawing in Model Space or the scale of the viewport in Paperspace. Previously if you wanted to adjust a value by the viewport scale in an expression you had to create a style for each scale or enter the scale conversion manually when the scale change. In 2009 the Drawing Conversion Scale will automate the task.
Another possible use of the Drawing Conversion Scale would be to make a block a constant size, regardless of the viewport scale. Or use an if then statement in the expression to vary the text height based on the viewport scale. This way a label could be one size for scales 1"=20′ to 1"=50′ and another text size for larger scales.