We are currently using the MW & DS Mapbook extensions concurrently in a single MXD to create MXD's that have 2 mapbook-enabled dataframes. For example, we have a map with a plan view that represents 5000 linear feet, and a profile dataframe with CAD data representing the same 5000 foot segment. We use index polygons in each dataframe to change segments. We also use this same methodology to create dual plan view maps featuring sequential sections of linear feature (road, levee, rail etc.). For example, in a single MXD, dataframe #1 contains station 0-1000, dataframe #2 contains station 1000-2000. These end products constitute a large volume of our work, however we are currently unable to replicate them in 10. Without this funtionality we will be required to have 9.3.1 installations instead of moving to 10.