I took piano lessons for 8 years and guitar lessons for 5 years. I worked at it quite a bit, but I still can't read sheet music or tabs without stopping and figuring out each note. It just doesn't make sense to me.
On a somewhat related note, I've noticed that games can be the same way. I could play Tetris all day: something about making the different shapes fit together is stimulating and makes something click in my head.
My friend just can't get a hang of Tetris though. He says his brain just can't compute all the different shapes in the amount of time it takes to get to the bottom of the screen. One day he picks up this cellphone game called "Galaxy Balls" which is somewhat similar to Dr. Mario. He's hooked on it now. I tried playing it for days, but just couldn't make much sense out of all the falling colors.
I think this is probably the same deal with music. This is why some people prefer tabs, others prefer sheet music, and some prefer something like Synthesia. Personally, a horizontal piano roll (I am getting used to Synthesia though) is the only thing that ever made much sense to me, even though I've been using sheet music and guitar tabs for much, much longer.