Try as I might, even if I dont forget to turn my phones ringer on, the trainers voice is not always audible (sometimes theres a break in the audio which is enough of a cue). The GPS is also incredibly inaccurate, as far as I can tell. Nevertheless, the apps drawbacks havent stopped me from finding it effective and motivating to use.
Kaz_8419 about Couch to 5K® - Run training, v3.3.7