It liberately employed specular maps at least (no idea whether they've used seperate maps, but you get the idea). That was actually pretty rare on the PS2 as well. For most PS2 games, effects such as metallic sheen was usually achieved via painted texture maps.
Cannot commend them enough for their heavy investment into the area of breast physics also
God, I loved that game. Sequel was pretty good as well and so were the Champions of Norrath games. I miss Diablo clones with bigger skill components. You know, games in which getting damaged was actually down to proper collision detection and not dice rolls.
I was also really impressed by other PS2 games such as Primal and Ghosthunter. Those haven't aged quite as well unfortunately.