Useful why? It's blocking stuff, that's great. I don't care how many things it blocks on a specific page. It make no difference to me while browsing. The little counter changing just looks like an annoying animated GIF in the corner of my browser.

I get that a subset of users would derive some pleasure at knowing how many things are blocked on every single website they visit or users who'd like to use it to troubleshoot a specific page that doesn't load when blocking is enabled (in which case having a quick right-click toggle to turn it on so users can use it to troubleshoot would be ideal), but I'd wager that most users do not. Users that want it on can turn it on. (cue subset of users responding that they either 1. enjoy seeing the count or 2. use it to troubleshoot the rare page that doesn't load as a result of blocking)