First, install sysfsutils:
sudo apt-get install sysfsutils
Second, edit the /etc/sysfs.conf. Add the following lines at the end.
#tweak trackpoint
devices/platform/i8042/serio1/serio2/sensitivity = 215
devices/platform/i8042/serio1/serio2/rate = 280
devices/platform/i8042/serio1/serio2/speed = 150
devices/platform/i8042/serio1/serio2/inertia = 1
run sudo service sysfsutils restart to try out the new values ..