Throwing is good, decent and really bad. Depends on build and throwing weapon you use.
Heavy throwing axes are excellent throwing weapons and actually good way to deal damage in general. Works wonderfully as backup weapons.
Jarids, Javelins, throwing spears are good, decent and slightly bellow decent.
War darts are also okay.
Cut throwing weapons are underpowered and generally bad, unless you're hunting low armored folks.
Stones?
I had MW Stones last night, made interesting build with enough wpf and 8 PT and I must say that... stones truly suck. Worst possible choice in game, I doubt there is worse weapon than throwing stones atm.
They are as good as much they cost and that's nothing.