IMO it does nothing - at least nothing significant. No difference in accuracy or speed...
Possible reason was greatly described by user Tomula on czech forum here: http://smartmania.mobilmania.cz/foru...222286#p222286
He found, that Qualcommu Snapdragon QSD8250 in Omnia does definitely not have GLONASS support, so this app is probably for future devices with new GPS chip. Some sources are mentioned by him: