Eink

In our business (publication production) we need to make a lot of changes on the fly with story placement, widths and number of columns.  Split/Span enables us to set an individual story (with headlines, bylines, subheads, etc. as a single object instead of two or three that can be moved and reformatted as needed.  Yes, we could use a separate text box for headlines, of course, but then instead of addressing a story as a single object (as we do today in ID) we have to address each element independently.  Just a bunch of extra steps and time on deadline when time is precious.
Until/unless Split/Span an option in Affinity's Publisher, it's just not a viable option for us.

Today I noticed a significant new update — 1.9 has arrived.  Congratulations Affinity team!  Also noticed span/split columns still not offered.  So sad.  
Our publication production house will keep our fingers crossed hoping that the next update will include span/split columns so we'll be able to join the Serif/Affinity family. Until then, alas, it's back to .indd.
Good luck.  Keep up the great work.

Rats!  Another update, still no span/split columns.
Hey Affinity!  We can't wait to start using Publisher with our shiny new Macs in our production shop, but still can't make the switch without Span/Split.
 

Looking forward to switching from Adobe to Affinity, but can't justify the change in our heavy production environment until Publisher supports Span/Split columns.  
Hey Affinity developers!  Is span/split on your drawing boards yet?  If so, let me know.  We'll switch as soon as it's an option.  Sadly, until it is, abandoning Adobe is just a dream.
 

We're a publication production house itching to escape the Adobe ecosystem.  Really, really, really looking forward to the day when Affinity Publisher offers "span columns" option as a feature.  Until it does, Publisher is just not a viable option for a production shop.