I did not have any idea what's going on with this plugin, until I update to version 2.x. Then I saw that every version after 2 is broken, and that the forum is full of requests for troubleshooting.
I looked into NGG 2.x code and saw thousands of new files, a new unknown framework and lots of mess. My server shows huge difference in CPU usage and a lot more queries than before.
I just can not believe that anyone could so quickly kill this plugin.
Respond on the problems on forum is always like: click on the report bug, try new beta version or "we will forward issue to developers". Who is that new developers?
Main and primary problem is framework, CPU usage, lots of request and queries.
Whether a new development team even know how much damage they did to users and the plugin?
They release new versions without testing, fixed minor bugs and do not know what their main problem. Interface is ruined. With the simple and practical interface, they have made a complete mess that is terrible buggy and slow.
So much time lost, and their work is for negative zero.
Do not install after 1.9.13 (only if you are a masochist!)
This plugin needs to be shut down as soon as possible (or get new developers) until it make more damage to users.