I've only just bought my license and am pretty new to the plugin, but one think that seems to be pretty obvious is the need to have presets for such objects as grass, gravel, parking lots, groves of trees...... i.e. anything that's pretty repetitive and pretty dense should be automated. even if the presets are for a spline of a specific size. Even if they may not do the job completely, they would at least give the user a good starting point.
Tool tips would also be very nice to have (not a huge amount of work).