The first section is all dual carriage freeway. Quite boring but, take about an hour to get to Pakenham for a refuel where prices are still quite good.
this section from Pakenham to Cockatoo is very enjoyable. Traffic is generally quite busy during business hours, but the road has some twisties, and from the roundabout near Pakenham upper to Cockatoo is some excellent sweepers and some tighter bends. Surface is generally really good - though can have a lot of leaf litter after windy periods. flowing corners
From Cockatoo to Woori Yallock the road is quite open, with nothing too special. I like this section of road as you can get along at a decent rate, and has quite a few overtaking spots. Traffic can be busy during business hours.
From Healesville to Alexandra is VERY enjoyable. The famed Black Spur covers the first section. Even at the sign posted 80km/h it is a great ride! After Narbethong it is a little boring, but still great scenery and great little places to stop along the way.