sprite movement will definitely look better when you use fractional values for position, otherwise you are snapping to the grid and getting the "jerky-feel".

rasterizers for line-draw and poly-fill can work with fractional position values to determine which pixels to light up.

the snap-to-grid problem is exacerbated if you are using scaled up pixel art for that chunky look, so beware.

I now see what you meant, thanks for the pointers, I'm sure I'll be able to fix the problem with this information, thank you.