The original poster shared only half the significance of the change.
The change from a strict hierarchy to a single specific quality, damage type, or material of the weapon (or in very rare cases, a combination of two) is indeed an attempt to recapture the "flavor" of damage reduction: werewolves are resistant to non-silver weapons, fey are most vulnerable to cold iron, skeletons are resistant to piercing & slashing weapons, demons are vulnerable to good-aligned weapons, and so on. As a number of people have pointed out, it's lame that all the flavor of the "special material" DR is completely lost once the party has +1 weapons at hand (or even ready access to the magic weapon spell). And the hierarchy of pluses introduces the ugly metagame element of characters rating weapons (and monsters) by plus rather than by the actual qualities of the weapon (magic, silver, piercing, holy, whatever).
But the second half is what keeps this from being a hose-job to the fighters. That's the fact that DR *values* are going down, almost across the board. As I shared at Winter Fantasy, the vast majority of monsters will have DR 5 or 10 (a few, such as the mighty pit fiend, creep up to 15). That means that the fighter who doesn't have the right weapon can still dish out damage to a DR monster, just not as much. (Can you say Power Attack?)
This second part comes about because, despite R&D's best efforts to create a wholly new DR system for 3.0, the fact that there were monsters with DR 20, 30, or even 50 made the system work just like it did in previous editions, which is to say, "If you don't have a weapon this good, don't bother fighting." I mean, come on, does anyone even *try* to fight an iron golem (DR 50/+3) without a +3 weapon? It might as well just say "immune to damage from weapons less than +3" and in 99% of the cases, it'd be exactly the same.
I've been using this system in my home game for a few months now, and after some initial adjustments by the characters (such as buying extra arrows, or swapping a normal weapon for a special-material weapon, or just buying a secondary melee weapon), the players have taken to it really well. The "bypass mechanics" have generally proven very intuitive to players, meaning that they quickly figure out from context clues what they need to fight particular monsters (though I'm looking forward to their first fight with a lich...)
