As I can remember, someone here asked some time ago about a stylus input interpolation for smoothing purposes. Like it is working in the Painter (or, may be, other software).
Now, when I treat with some Wacom issues in my system, I accidentally found an interesting parameter in the xsetwacom. It is RawSample parameter, controlling the interpolation samples (or supersampling, or anti-aliasing) from raw input data to the resulted output (what we actually see). This can be easily changed, default: 4, range of 1 to 20.

So, for a "super-smooth" drawing it can be set to something big (I use 12), for "just smooth" something like 8, for default 4 and for "extra-sensitive" the minimal value 1.

The command for setting value looks like this:
xsetwacom set "Wacom Intuos3 6x8 stylus" RawSample 8
where ""Wacom Intuos3 6x8 stylus"" is your stylus device name, found with xsetwacom list devices
and "8" is the value.
For convenience, I create some scripts with appropriate commands and create launchers for them.

I'm sorry, if this information is already here, but i can't find it. Hope, it may be useful.
More information on The Linux Wacom Project


PS: Was tested on Kubuntu 12.04

Interesting! I'll test it as well -- I'm wondering how it really interacts with Krita, and whether it might be the explanation for the slowness with some versions of wacom drivers on Windows.