I did it several years ago, its fine so long as you DONT try and race along it, there are some sharp bends and steep (stream) valley down and upgrades that you should just take slowly and carefully, you bottom out quite easily if too fast
besides, its a splendid ~250 km with lovely river sightings and places to stop, picnic and or camp (at the community campsites) which are safe and some supply wood.
we took two days of leisurely driving stopping and enjoying.
NB, last fuel is at Ruacana so make sure you have everything full. Fuel is sold along the road at double the price and in old water cans or from dubious drums so make sure you are fully supplied before venturing. we camped at Epupa lodge and campsite with splendid views of the river, hot (solar) showers and a great bar and restaurant, as the Epupa community campsite was still "under restoration".
Take a nice long walk along the ridge above the falls so that you are perpendicular to the face of the falls, water flow is dependant on the flow needed through Ruacana power station so varies by time of day
be aware that the falls are unfenced, and the walkways are slippery in the mist, so take care while enjoying a magnificent unspoilt part of a wonderful land
Please report back on availability of reliable fuel and supplies at Epupa on return, please
Regards
Gordon Chunnett
083 455 7981