Migrated from Tampermonkey after learning that it was closed-source (and some other questionable privacy practices). Violentmonkey works great! All of my scripts ported over with no issues.

Works just fine for my own scripts and seems less complicated and more intuitive than the original GM.

a good quote:
If you need compatibility with old scripts your best choice is Greasemonkey. If you need it for modern scripts or to write your own Violentmonkey is fine. Avoid Tampermonkey, they are not to be trusted (proprietary license and analytics)[1].

[1] https://www.reddit.com/r/firefox/comments/6hs59w/tampermonkey_has_google_analytics_enabled_by/

Works perfectly, and adding scripts is super simple. I highly recommend this over the more popular Tampermonkey, which is closed source, and Greasemonkey, which is now rarely updated and lacks features.