At beginning I was annoyed to get some low review based on nonsense reasons or something not depending on me (I have got 1 star review because internet connection drops when user switches from wlan to 3g), than I stopped caring so much about comments since there is nothing you can do. You may put developer email address, support webpage, but still some users will ignore it and low rate your app, showing no respect to the hours of work you had put to develop the application.