You seem to have a few problems 'hitting' the lines. That happened to me a lot when I was using a Bamboo, however it improved over time. Like dadevster said, it takes a long time to get good at it, and aside from the knowledge about proportioning and all, you'll have to learn drawing almost completely anew. So far, you're doing a very good job - you don't seem to have anywhere as many problems as I had ^^
As for the line accuracy, I tried to use that as an effect before in
this drawing, which centers focus to the facial area not only because of more lines in that area, but also because those lines are drawn far more accurate than those in the rest of the picture. You can see I messed up on the ear part though ^^"
All in all, you have to keep practicing, and I don't mean practice regular drawing: The pure fact of getting your hand used to the tool requires practice really, but once you have it, it's a very cool tool in many media applications, not only drawing!
As for the button layout, I think all Wacon pens have two buttons on the side? Either way, I have the lower one (closer to the tip) set to right click functionality, while the upper one is set to 'Undo' in applications such as Photoshop or Illustrator (this button mapping will not only ease your workflow, but also make you cooler when drawing somewhere outside, as you don't have to use your keyboard much :biggrin: ), while mapped with middle click functionality for all other programs (I dunno if the lower-grade Wacon tablets support application-based mapping, but they should really...).