So far, I have only used this with available indoor lighting inside my apartment. In areas of my apartment that metered between 10 to 60 footcandles LightMeter gave me exposures that were consistently two full stops too dark. However, in two areas that metered at 5 footcandles and less, LightMeter gave me good exposure readings.
Also, when I first installed and tried to use the app, I kept getting a message something like "not enough available memory to take photo". Shutting down and restarting the iPhone resolved the issue.
For $3.00 I guess two stops isn't too bad, but I hope a future update may resolve this issue.