At 30 its just 15% more damage and less stamina usage , that not much for the last thing
I really notice in minning when its in lvl 70 , you can break a iron crap in crypts in 1 swing
Where u are really notice from 0 to 100 its in running and jump
For weapons at 100 gives 50% more damage and less stamina usage but take time to lvl up weapons high
You can notice the damage buff in the weapon stat : 40 ( xx ) <-- here is the total damage of your weapon with your actual skill