Probably the best ... Canon Speedlight to be reserved for experts

This speedlight incorporates an impressive array of functionality and a rear display of exceptional readability. No need to waste hours learning the meaning of complex symbols: everything is accessible and configurable flash back. Recent devices will control most settings directly from the flash menus. Obviously master and slave speedlight, it can control up to 15 radio speedlight flash.

The construction of the flash gives confidence and caoutchou around the claw makes it resistant to rain or dust.
The number of guides can track my 70-200, up to 200mm.
It comes with support for color filter and a pretty pouch incorporating a filter white and orange. The flash is informed of the presence of a filter via a connector under the head. Therefore it can project a light of a color compatible with other light sources.
The refresh rate is impressive.

In short, an excellent product, but the price, size and "complexity" Subject to an informed public.