We went across the Botswana-Zimbabwe border in both directions on that road in September and, contrary to what we had been told, the crossing formalities were speedy (certainly by African standards). Apparently they've recently revised the arrangements on the Zimbabwe side and it's a lot more efficient.
There are still a lot of roadworks and queuing lorries around the ferry (eventually to be a bridge) crossing in to Zambia on the Botswana side, but we got through that section quite quickly, too.