Our approach was almost exactly the same as what Camila had stated above. That said, I wanted to pass along a few things that we learned outside of the rollout.
1.) Preview for Individuals actually caused more problems - While the preview was tremendously helpful to a small group of people like our central travel team and myself, because we could toggle back and forth to get comfortable. Employees out in business units actually struggled more when we transitioned them early, as many of the people that they worked with were still in the old UI and this created a negative perception from the outset for those users.
2.) What hasn't changed has become a problem - The approver view has not changed. This means that approvers are having to operate in the old view/function when approving and in a new view when working with their own travel reports. This is not popular and, in fact, difficult to manage. I would encourage you to focus energy with approvers, so they know that they will have 2 views. In a few cases, we have temporarily assigned proxy user access to certain approvers that were struggling with this, so they could open a separate browser and proxy users in one browser while handling the actual approvals in a separate browser. The same sort of holds true for processors, as they too work in two separate views. However, this group is so accustom to navigating through the system that their adjustment has been less.
