Hi!
About loosing precision: there is already noise (jitter) in real-world devices so that you can't achieve subpixel precision anyways (unless your panel has a very low resolution). Please see my answer to Dmitry some mails ago.
Maybe you can achieve better precision with averaging.
Anyway "input is already noisy" does not mean "so it is okay to degrade it more". Solve it properly. That means passing calibration data from kernel to userland.
Thanks, Pavel