I have noticed that in MEP 2010, many small things such as label gaps, are now paper space based.
With this said, as of now, when you go to the duct display properties, under the "hatching" tab, the scale/spacing is not annotative, so if you set the scale/spacing to 100, then it will be fine for an annotation scale of 1:100, but if you change the annotation scale to 1:25, then the hatch scale/spacing will be way to big, so you will have to manually change the hatch scale/spacing everytime the annotation scale is changed, and individually for every duct that is hatched. Another nice idea related to duct hatching, is to be able to select multiple ducts and elbows, and be able to turn on the hatching for all of the selected at once...