Have bought a super bells yellow every year since 2008 so I didn't know what to expect with the "new for 2017" ad.
So far 2 improvements stand out for me:
1. Branches are stronger and sturdier.
2. Flowers are somewhat larger.
I have 2 of these new for 17 editions and am very well pleased. Each shares a pot with other PW plants and is thriving.
Both get only afternoon sun, about 4 hours direct and then late day shade.
All I do is water regularly and fertilize every 10-12 days.
They spread and mound equally well so they can be used for spillers and fillers.
Only downside...this year the Japanese beetles have added some of my callies to their diets but damage has been negligible.
Aphids, on the other hand, love to munch on callies so I have to keep close watch.
Still I highly recommend this plant as the yellow is as good as it gets, the blooms last a while and there are dozens on them all the time.