It works fine, but is limited to +/- 5 seconds, you can't move subtitles more than that, so that's an issue when the actual delay is >5s. Also, you can use mouse only and you need to click each time to move the time by 0.05s, and each time pauses / starts the video. My tips if you'd like to work on this - otherwise very useful - addon:

1. Expand the limit to more than 5s, od disable it entirely
2. Enable the field to enter the time value manually
3. Enable the slider or remove it entirely, it's impossible to adjust it for all needs.

Thanks for this, very handy tool :)