I have a similar problem, only it gets worse when I'm resting my hand on the tablet next to the lines (click for large version):
(Tablet is lying sideways. The two leftmost lines were drawn without my hand, the others were drawn with my hand resting as shown. Same effect with right hand and lines to the left of my hand.)
This effect only appears when a large part of my hand is resting on the display (a fingertip is not enough), and if the area resting on the screen is "pointing" along the pixel grid lines (up/down or left/right, but not diagonal). The squiggles appear only on the area next to the hand (where it is "pointing" to) as seen on the picture: the lines are less squiggly at the top / bottom. Also, when I put a towel between my hand and the tablet the effect vanishes, so I don't think it is because of the pressure of my hand bending the device.
I am assuming the electronics for the capacitative touch screen conflicts with the stylus in some way. The touch screen electrodes are faintly visible as a horizontal / vertical grid pattern, so it would make sense to me if these electrodes get overloaded in some way by being in contact with too much skin, and then go on to interfere with the stylus sensing part. I don't think it is a problem from anti-aliasing, since the resolution when drawing is actually quite high.
This does not only affect lines, but any kind of shape becomes "bumpy". Because of the way I hold my hand while writing, it can become quite irritating, unless I put a towel or similar below the palm of my hand. Is this a problem by design (does anyone of you have the same problem), or do I have a defective device?