I agree. It will keep getting better and I would much rather have these things available than not. It would be cool if the site provided the raw ffmpeg command line so that you could use it as a command builder and run it locally for large or batch jobs. Then you can choose between security and convenience or max performance.

The notes you mentioned sound like fundamental ffmpeg issues rather than problems with the implementation of this tool. It can usually trim without transcoding (much of) the file and encoding VP9 is notoriously slow.