I use CS4 when I do Photoshop stuff, which is increasingly less. I’m doing more and more inking in ArtRage, like those mermaids today, which I think makes the lines flow nicer and it has more variation of thickness.
In any art program, check the hardness level of the brush you’re using. It might be set to something slightly fuzzy and you don’t even know it. Also, in Photoshop, in your brush options, go to Brush Tip Shape and set Spacing to 1%. Actually, that’s probably it. The default is always like 25% and it makes things slightly wiggly. I always turn mine down to 1%.