I would certianly find this feature useful and can explain the concept...

My company make 3 different types of sale - Products, Services, Support - for example.  

I have added fields to my Deal Details section to capture information about these sale types. 

Currently all fields show and sales people have to know which fields to fill in and which to leave blank for each sale type.

I would only like the fields pertinent to each sale type to show when the sale type is selected.  This could either be as a result of a selection in another field or by adding a label to the deal.

Could anybody else make use of this feature?