For us, the issue is that our entire Salesforce experience is in Lightning, but quotes is only functional out of the box in classic. So, an end user can access the quotes section in Salesforce Lightening interface, but must switch back to classic to have a functional quotes interface. It's incredibly disruptive to the workflow to shift between the interface styles. It's not a matter of using it on an iPad or that it's cool – interface changes in the middle of a billing workflow is a high friction event and really unpleasant for the user. Lightning is a significantly better user experience and Zuora quotes would be much improved (and useable to a Lightning based organization) if is was fully available in that form.
... View more