The annoying part of working with SearchWP on a large site was waiting for the search index to rebuilt. Working on a site with over a thousand Woo Commerce products with often lead to a multi-day rebuilt time for the search index. This made troubleshooting and debugging a slow and expensive process.
After upgrading to SearchWP 4 from SearchWP 3, index rebuilds on the same site takes less than ten minutes. This allows me to make modifications and changes for clients much less frustrating. I expected improvements with the new version though my expectations have really been exceeded.
Along with making work easier, the SearchWP interface has been updated giving a more intuitive layout. Still my whole approach to website creation is to avoid the need for a plugin like SearchWP in the first place. However, with this major update, websites using this SearchWP 4 will see some major improvements.