Rating: 1 star

NextGen Comments is (at the moment) just a function library for developers
Don’t enable this plugin, and expect anything magical to happen.

On the plus side, it appears to give a functional framework to write and retrieve comments from the standard WordPress database using standard functionality – no new tables are created by this plugin.
This is a good thing – if developers use this approach for NextGen comments, then it makes things more compatible across different themes & templates.

However, there’s no documentation (at present) – including usage documentation – and no Javascript functionality to link the library to a front-end template. The plugin’s not been updated for a year, so it doesn’t look like this is going to happen.
(The lack of documentation is the reason for my 1* rating).
There’s no admin functionality built-in either.

So if you’re happy coding around this (and I’m going to try), then it looks like a good structure.
But if you’re looking for something ready-to-go, then you need to look elsewhere.