Thanks, [MENTION=13650]AeroDm[/MENTION] - you put it pretty well. I don't want characters to suck, but I don't want characters to outshine one another too much. There's a certain power level that I tend to like in my own characters, and when I see other players building characters that I feel are significantly above that power level I tend to feel like they're all about power and not at all about character.
I'm doing it right, and everyone who loads up on power beyond that level is doing it wrong.
The odd thing is that I don't look down on players who build characters significantly below that power level; I might offer to help them, or I might try to tone things down in my own character so that the others get to shine, too, but I don't feel like they're doing it wrong.
For instance, I've built characters in D&D 4th Edition that put an 18 in their key ability score before any racial bonus. And I've felt dirty in doing so. I understand that it's optimal for a lot of classes (the Hunter and the Thief, for instance, really have no reason not to max out their Dexterity), but it feels... wrong somehow.
Perhaps I value balance... yes, I think that's probably it. A character that's optimized just around combat is unbalanced in and of itself. If that character tries to do anything other than their one big thing, they're going to be pretty lousy at it. Of course, in a well-balanced party that's okay - the other characters pick up the slack in those other areas. I still feel judgmental toward those optimized characters despite myself, though.
Anyway, I feel like I've gotten some useful perspectives on this question now. In the end it's largely a question of putting the right groups together. If you've got an optimizer, make sure they're in a group with other optimizers. If you've got players who don't focus on building optimized characters, make sure they're in a group with one another. Mixing them... well, it's probably best not to if it can be avoided.
As for me, I'll adapt to my group. If I'm playing with optimizers, I'll join them in the min-maxing. If not, I'll play to the style I prefer. Unfortunately, I know that I'll be in some mixed groups, and I'll muddle through as best I can.