Users appreciate the Ad Inserter plugin for its effectiveness with Google AdSense, ease of use, and its ability to handle complex ad placements across multiple websites. It simplifies ad management and offers extensive customization options, allowing ads to be placed almost anywhere on a site. Additionally, it provides functionalities like hiding code on mobile devices, integrating well with AMP pages, and adding codes to headers and footers. However, some drawbacks include a confusing interface, performance issues on shared hosting, and the need for the Pro version to access advanced features like geo-targeting and ad statistics. Despite its minor flaws, it remains highly recommended for both beginners and experienced users.