Canon will soon release a firmware upgrade for the EOS M that will boost the AF speed, making One Shot AF up to 2.3x faster. The new firmware will deliver improved performance as a result of a reworked AF Drive Control System. Canon will be releasing the firmware update in the next few weeks.
Below are videos showing off the performance of the EOS M and the 22mm lens with current firmware and soon to be released firmware.
Current firmware :
New firmware :