Fountain pens suck on this paper.

Actually, I'm just being pissy, the paper is fine for watercolour in particular.  I just lack the patience to have the pen deposit it's sweet carbon filled liquid in a timely manner.  The bouncing on the bus doesn't help too, but it really does force me to wait and pay more attention to what I actually want to put down [waiting at traffic lights falls under the classification: "Golden Sketching Zone"]

I actually swapped around with a few pens/pencils for the top sketches since I had lots of stationary time... ooh, that would have made an awesome pun.