The international Baccalaureate uses a 7 point scale: http://www.isnsz.com/media/images/Assessment_6.width-800.png

I generally like my scales to be logarithmic. At work, I made the following scale to explain difficulty of technical items to non-technical people. It works quite well:

  Effort Scale

  1: Easy peasy
  2: Trivial but time-consuming
  3: Some invention required and non-trivial
  4: Invention required
  5: Lot of invention required 
  and for special occasions:
  6: This is a whole new startup

Yelp and Uber ratings, and other 5-star ratings bother me. There is no generally agreed upon standard. Sometimes people give 5 stars only for exceptional service, however, most of the time, people give 5 stars if they weren't wronged in any way. It's a mess! Also, most people aren't qualified to differentiate between five different levels of service/food. It should either be generally agreed upon logarithmic scale, or it should be a yay-meh-nay scale with no guilt in giving a meh.