As with the multitude of updates that came before it, update 1.09 works at making Bloodborne a better experience for players.
The biggest change the update is doing is allowing players to buy Blood Rocks from the Insight shop. A Blood Rock is required to upgrade a weapon to its max level, +10 strength, and prior to the patch, only one Blood Rock was available per playthrough. With the Old Hunters DLC, an addtional Blood Rock was able to be found. Players can now nab additional rocks for 60 Insight each (the patch notes say that a certain part of the game has to be completed for the rocks to be purchasable in the store, but doesn't say what the requirement is).
Additionally, the price for Blood Stone Chunks, which are used for upgrading a weapon to +7 strength through +9 strength, has been dropped from 30 Insight to 20 Insight. The update notes also state that the strength and stamina values for several weapons have changed, but don't specify which weapons.