I think it really depends on the comfort level of the user with their OS.  JoinMarket does require a connection to a full bitcoin core node, which may be an obstacle for some new users.  For those comfortable with or currently already running a bitcoin node, I think the install documents are pretty detailed and well written. 

Personally, I think Jamapp.org is a great product for anyone comfortable using Linux based operating systems.  The Windows installation is also very straight-forward, and most people are probably using Windows.

While JoinMarket is a 'power-user' type of tool, a lot of effort has been made to make it easy to use and understand across a wide variety of situations.