Sorcerer's Place has conducted an interview with Obsidian Entertainment's Ferret Baudoin, quizzing the lead designer about the 3.5e rule changes they are implementing into Neverwinter Nights 2. A snip:
Q: Are you making any significant changes to any of the monsters encountered in the original Neverwinter Nights and the expansions based on the 3.5e rules upgrade?
A: The biggest change for monsters is that in 3.5 edition damage reduction has changed dramatically. In 3rd edition you'd have damage resistances like (5/silver). That means that you'd need a silver weapon or any other magical weapon to do full damage to that critter. The problem is that magical weapons are pretty common items to adventurers so very shortly all damage resistances that aren't dependent on how strong the base enchantment on your weapon is become irrelevant. But 3.5 changes that and even a +5 longsword will not fully damage let's say a werewolf. It makes a big difference for certain creatures.