I've used lots of these pens and the 0.04 is the best balance between a fine line and smooth writing. The 0.03s that I've tried have all been scratchy.
moonfirespamThanks for your input, I might just get the 0.04 instead then. @andy I meant 4 pens each of the three pen types (4 of hyper/micro/ultra etc, to 12 pens total), since it'd be cool to try them all :D