High speed sync is cool if you are trying to use really high shutter speeds, for example to freeze motion, or trying to reduce the exposure if you are shooting into the sun or another really bright light source. I have tried to use it a few times with my 430ex ii. It is fun, but I honestly don’t find much use for it. Maybe others do.
The commander mode, if you have, or rent other flashes to use in a multiflash setup is important. I get around this with the ST-E2 controller. The Yongnuo ST-E2 is just like the canon version.