RE: the "writing things down" discussion- personally, I would hope we all aim for the middle ground.
Penalizing the PC, and thus the party, for things outside of the campaign world is, IMHO, bad DMing. Getting lost in a maze (because nobody mapped it) is one thing, but assuming that a PC can't remember what a player has forgotten is quite another.
My personal experience in this was a campaign in which, as we are closing up the session, packing up books etc., we are still discussing "in game" issues, including how we were going to gear up for the next adventure, putting in orders with weaponers, armorers & alchemists, and trying to figure out the interaction of a bunch of symbols we encountered.
Then, in a flash of extraordinary insight, I "connected the dots" of the symbols together and blurted out the answer of the mystery they represented- the DM said I was correct- and we broke up for the holidays. Nobody could game from Thanksgiving to after New Years.
When we next met in mid-January, one day of campaign time had passed, but, of course, I could not recall nor restructure my deduction. Because I had not written it down nearly 2 months previous (while trying to vacate the host's house), my PC was deemed to have forgotten the info.
This ruling, BTW, came courtesy of a guy who (as a player) loses his character sheets every couple of months.
I griped for a few minutes, but let it slide. However, the campaign didn't last long after that- apparently it bugged the others a bit more than it did me...especially since the DM didn't remember the prep work our party had told him we were going to do.
RE: Playing in character.
I do that as much as I can. I've had my Druid/Rgr/MU threaten another player's "archmage" with attack if he loosed his megafireball at the undead in the forest...because of the effect on the forest.
I've had my formerly-artifact dominated PC rush to grab said artifact to rescue it from destruction by another PC...despite the fact that my PC was toting Mordenkainen's kid, fresh rescued from cultists. The kid didn't survive the artifact's destruction.
If you're not playing your character true to him or herself, you're not roleplaying, you're metagaming.
The "Your Cool Character is Broken" Guy
I play with someone who always complains that the other characters are too powerful due to some rule loophole they are exploiting. He never bothers to analyze their weaknesses, just sees their strengths.
I'm still gaming with a guy who hacked me off royally one night. 2Ed Player's Option rules- we're both playing Priests (in an 8-man party). He went for the spellcasting unarmed & unarmored combatant path, with powerful combat spells (including some Wizard spells) from a couple of Spheres (Major Access) and almost no Minor access. I delved into Finno-Russian/Kalevala mythology and came up with an armored Northman Ftr/Priest type, whose spells were all taken from the weaker Spheres- all with Major access, plus Wizard Abjuration spells...and no turning ability. He took one look at my massive spell list and went into MAXIMUM HYPERWHINE "Fighter Armor, weapons, HD & THAC0? Major Access to all those spheres AND Wizard spells? You're playing SUPERMAAAAANN!"...without realizing that of all my spells, only 3 were offensive...and one of those was Bull's Strength which would be cast on the true fighters.
I just looked at him and just ripped up my PC in his face, rolled up a Ftr/Thief in 5 minutes and played that...quite the back-alley thug. However, that player ticked off the DM to the point that the DM ended the campaign...right before my Ftr/Th could kill his PC.
(My notes on that Finno-Russian PC survived- I "resurrected" him for another campaign that started up a month after the other had started. He died in the first combat due to a crit by a skeleton with a 2 handed sword. No kryptonite was involved.)