Wow, okay so I just spent a whole day using this Rotring 600 0.5mm mechanical pencil and no, sorry folks, this is definitely NOT a comfortable pencil. Do yourself a favor and save yourself the money and get something else. I go through 5 years of electrical engineering to get my degree using a Zebra M-402 mechanical pencil and it was worlds better and more comfortable than this Rotring.
http://www.amazon.com/Mechanical-Pencil-Refillable-Silver-ZEB59210/dp/B000X0VXT4/
http://www.amazon.com/Mechanical-Pencil-Refillable-Silver-ZEB59210/dp/B000X0VXT4/