While I don't write in grammatically correct form all the time, I do try to adhere to most conventional rules. That being said, one of my biggest pet peeves (and, admittedly, confusions) is the thin line between good and well.
In my junior year of high school, my nun AP English teacher impressed upon the class that we could be "good in bed," yet it was grammatically impossible to just be "good." Instead, the proper answer to a question as simple as, "How are you?" would always be, "I'm well."
Recently, there was debate between my friends and me as to whether this was fact or merely fiction. Having a solid grasp on the difference between adjectives and adverbs, I felt (and feel) that this is an inalienable truth. For me, good will always be an adjective, while well will always be an adverb. I dislike using good as an adverb, though I understand at times it can be used as one. Still, I fell that while you can be "good" at something, it is grammatically impossible to just be "good."
On the other hand, you cannot be "well" at something. You can be well, and well is appropriate in many circumstances. I personally dislike the response of, "I'm good," following the question of, "How are you?"... but then again, I HATE the question of, "How are you?"
In German, that question does not exist.
But I digress.
If "How are you?" must be asked, I believe there is only one appropriate answer in the realm of good/well. That answer for me, obviously, would be, "I'm well." Theoretically, it's grammatically impossible to just be "good." You can be "good" at something (ie, "good in bed"), but you cannot just be "good." Good is an adjective, by definition. Well is an adverb. Case in point, as stated.
Argue all you want, but if you truly stop to think about it... I'm correct.
Just this once.