Originally Posted by: ren... I personally have never used the actual 'circle of fifths' in visual form ...

In my experience the single biggest reason guitarists have a hard time with the circle of 5ths is because it is hard to visualize on their instrument. Literally, it is hard to SEE.

This is because the guitar makes no physical, visual distinction between a natural letter note and a sharp or flat. It's just another fret - one up or down.

Compare this to the piano and immediately the difference becomes obvious. If you are playing in G major on a piano the only black key you see and, or play is the F-sharp. Because the piano has it's very distinctive pattern of white keys for naturals and black keys for sharps/flats it is easier to see and recognize accidentals and key signatures.

Another problem is that many guitarist simply refuse to learn how to read music. The more a player reads on a regular basis, the easier it becomes to understand, see, and use key signatures, and thus the circle of 5ths.