Summary: If you need related posts just to entice your readers, this plugin is a great fit. If you also want related posts for your SEO, which is often the case, don't use this plugin.
The nrelate plugin immediately left a good first impression when I opened the plugins page on WP.org: it clearly state what it does, and why the author thinks it better than other plugins for the same purpose. Turns out, nrelate is not your average plugin, it comes with a service from their side that spiders your entire site and analyzes all the content, so it can not only show related posts, but really show related content from all over your site.
If there’s one thing other plugin developers can learn from this one, is in how much thought has gone into the plugins page on WordPress.org.
When you install the plugin, it automatically begins indexing your site. To be honest I think it’d be better if it told you again and asked for permission, since it will send data to the nrelate service, but ok. On the dashboard page it shows you its progress and on the settings page you can determine whether you want to show related content with image and text or with just text, and also what size the image should be.
The shortcode is registered in the way its supposed to, but it inserts inline styling no matter which way you use it, I would not want that, so I’d like an option to disable the inline styling and instead add a class that I could add to my CSS file. The same goes for the iframe: it has inline styling on it.
Another issue is that the plugin relies on CURL for it’s workings, instead of using the WordPress HTTP API, something that could cause issues on certain hosting environments. Overall the code quality is pretty ok.