I just finished the Champions Ballad and for what it was, it was an amazing add-on for the game, and along with DLC1, this was definitely worth the $20.
The added costumes and gear was pretty cool, my favorite of the bunch was the Phantom Ganon outfit and the Wind Waker lobster shirt. The Royal Guard set with the Hylian Hood is a nice touch as well.
The added cutscenes, memories, and final memory with the Champions was done really well. While they did add some backstory to the Champions, I wish they would have actually added some more story to the game, and I was even hoping for something post-ganon as well. Hopefully there will be a DLC3 which expands on the final cutscene where Zelda wants to make some adjustments to Vah Ruta.
Difficulty wasn't too bad. The 1/4 heart trials with the Obliterator was an interesting challenge, I've had some of the funniest deaths I've had in awhile. The added shrines were hit and miss. The general defeat a foe, race through rings thing got repetitive after awhile. The actual shrines themselves were a nice treat, as well as Link's Divine Beast dungeon.
The final boss fight was a welcome change and a nice twist. He wasn't terribly difficult, and showed us what kind of fight Master Kogha should have been. The Master Cycle Zero is ****ing RAD. Everyone has their opinions of why a motorcycle is in the game, but if you think about it, the Sheikah Slate is basically a smartphone with a camera and rune-apps.
I thoroughly enjoyed the extra time and dialogue we got with the Champions. Each one got some added depth of character. Seeing Urbosa wreck some Yiga clowns was amazing, Daruk being frightened of a dog was hilarious, Revali didn't surprise anyone with his competitive attitude towards Link, and Mipha's extra dialogue to Link after beating the blight multiple times just adds to her tragic love story with Link. Seeing Zelda have fun with the dog was pretty cool as well, and the final group photo scene was incredible. Purah yelling at everyone to adjust themselves was great.
For an expansion, this was done well once you got past the Obliterator challenges. The added gear, cutscenes, and backstory provided further completes Breath of the Wild, a game that needs as many story elements as possible.