I find there's often an inverse relationship between tin note and taste. The ones where opening the tin curls your nose hairs tend to taste great, and the really tasty-smelling tin notes often disappoint when smoked. Not always, but much of the time.
I don't necessarily agree (though I've certainly had what you describe happen), but this brings up an interesting point.
Does the tin note really matter to you?
I find it does to me, and I don't know why. It seems to me that the tin note of tobacco is basically smelling a cake before it's cooked... it shouldn't really affect my opinion of the tobacco.
But it does seem to matter quite a bit to me--I suppose because pipe smoking is a bit of a ritualistic experience, and the tin note is part of that. Some blends I've gotten, I really liked even though I didn't like the tin note, and it really bothered me.