The roads between PP, Siam Reap, and Preah Vihear are are sealed good road for the most part. The last 40kms near PP being the worst with much construction going on.
As far as experience goes take it slow. Once you gather experience still take it slow and expect anything and everything. The people you have to really watchout for are the shinny new Lexus drivers drinving down the middle of the hwy at twice the safe safe speed.
That said there is much more give and take in asian driving style. Much less passive aggressive behavior or outright aggressive behavior towards motos, than you see in western countries.
Traffic justice is often done locally. Where the driver who hurts someone is dragged out of his vehicle and beaten to death by a local mob.