There were a couple posts recently about game balance, a topic we love to beat to death. Tim at Gothridge Manor saw these and just came out and asked how we as players feel about game balance. He specifically mentions the kind of "game balance" that adjusts encounter difficulty to match party strength. Also, Peter at Dungeon Fantastic asks, is fleeing a dangerous monster really the proper response? After all, old school characters are disposable, which is why the old school is so gung-ho about abandoning balanced encounters.
OK, I'll bite. As a player, I'm probably more concerned about PC vs. PC balance than PC vs. encounter balance. But the same principal applies to both: I only care about extreme imbalance. I hate the kinds of classes that seem to be designed for munchkins, with lots of powers and no real drawbacks. Not only does this mean that there's no risk of losing my character if I or one of the other players chooses such a class, but the existence of such classes brings out the worst in some players: either they pick such a class and try to dominate the other characters, or they dominate the players, demanding that everyone play at a cranked-up, highly optimized level.
I hate the same thing in encounter balance: if the GM is obviously cranking up every encounter so that the choice is between "super deadly" and "mega deadly", or if the GM resists PC attempts to discover details about the target area beforehand, so that we can judge which risks we want to take, then I'm not happy. I'm OK with some encounters being too dangerous to pursue. I'm OK with fleeing.
And that's not because I think my character is special. I don't think most people in the OSR believe in "disposable characters", not in the sense of "you should never care about your character". Sure, the DCC game seems to embrace that, but even there, I suspect the intention was that characters should flee when an encounter goes against them. Why? Because the deadliness of an encounter becomes meaningless if you don't want to avoid death.
What I think some people may refer to as "disposable characters" is the attitude that your investment in a character should be based on actual play, not on pre-game planning. Your character isn't a special snowflake, but it's not cannon fodder, either, at least not from your viewpoint. Your character becomes more interesting as a result of facing dangers and either fleeing or winning the challenge. The longer you play your character, the longer your character remains alive, the more important that character becomes. The Raise Dead spell was available from the very start of D&D, after all, just not to new characters.