Now using this metaphor of My PC = My D&D Sword of bonuses I want. One could argue that if all I have is a crappy PC, I should use a lighter developer tool. Technically I can write a program on the computer. However, to solve the problem at hand, I actually do need a more powerful PC.
The same goes for magic swords. Sure, I could stick to killing rats and goblins with my non-magic sword. But if I am actually confronted by a level appropriate monster that has magic requirements to hit (silver, +1, etc), then I actually do need a proper magic weapon.
D&D has ALWAYS suffered from this concept. Werewolves always needed magic or silver to-hit. Other monsters always needed magic of a minimum + to hit. This meant that if the PCs encountered it, they HAD to have the item or were probably screwed.
Right. However, I think you are concentrating more on the boundary conditions while I'm talking about the stuff in the middle. (I say this with VS 2010 also eating up my RAM as I type.

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I think most of the arguments have traditionally been about the boundary conditions, and I already see Jester's response to your post, which is talking about the same thing. Basically, there is this boundary "zone" on each end of the efffective range where your characters are definitely sub-optimal or super-optimal, but still have a shot. This is analogous to me using a wrench to drive a nail, or using a nail-gun to drive six nails into a single 2x4, respectively. There are thing that you might do isolated that a professional won't repeat, if they can avoid it--i.e. struggling or overkill. Naturally, people have different places where they draw the exact line in the boundary zone, and every situation is different. I can easily conceive of situations where I would fine confronting the party--having no silver or magic weapons--with a werewolves to be entirely fun and fair, or not.
But what I was more interested in is that band in the middle. If there is one. Maybe that is my question and you are answering it in the negative, because of the frequency of the boundaries? That is, how often do we have a fight where +1 weapons are entirely adequate,
no matter what the situation, but +2 or even +3 weapons are nice to have, not ridiculously over-powered, etc? I'm fairly certain it happens in isolated incidents going from +1 to +2, or similar, but how often? How often do we get to a point where
any reasonable conception of "necessary" has been met, but their is still room for maginal tool improvement outside of character skills?