One Way to Get Reviews
Getting good reviews and avoiding bad ones is crucial to your success. I hate to hound users for reviews while they're interacting with the app and it can be very difficult to get reviews regardless of your download numbers.
So, how do you get users to email instead of just leaving a one star review, or to even leave a review at all? Users will usually take the path of least resistance. Make sure you have a 'More' view in your app that has a button with a title like 'Problem or Idea'. Allowing them to vent a complaint lowers the chance they will vent in a review for everyone to see. When they email you with the complaint or feature request, always ask nicely for a review. Many users are excited that someone emailed them back and will often make an effort to leave a review. My personal favorite support emails are the one liners that say something like "I hate your app".