Some good and some negative points

The caching is quite good. When it comes to speed W3, Rocket and Hummingbird have almost the same Performance on my server. The setup and navigation takes some time and could be clearer. In addition, it takes a very long time until the assets are generated. But they have quality and you can also set manual rules yourself, which is a plus! A big minus point is that Hummingbird does not remove the entries in the Htaccess file when you deactivate the plugin. This is really bad and should be fixed. If you don’t know enough, you don’t notice this and then have multiple entries from caching plugins when you switch. A big plus is that also queries are cached, so also the filters on the store page! I do not know, however, up to what extent with many taxonomies.