My take is covering is not too hard. Covering really well can be challenging. I've always aimed for well enough that I wouldn't be embarrassed. Anyone who reads this and has actually seen one of my planes (there are some here on RCU) is free to comment on whether I've met my objective or not.

Edit: A good teacher really helps. I owe all that I know to a gentleman named Dave Guerin who taught me many years ago. I only wish I could finish (or build or fly) planes as well as he can!