A great drive - whether you're going in for the day or staying a night or two, getting to milford sound is half the fun.
The drive starts off easily enough but by the time you get to the hommer tunnel you're thinking "what am I in for" and then the descent on the other side leaves you thinking " eek"! You do wonder how you're going to get your large campervan round some of the cornes down (or up) the steeper gradients - but then you remember loads of large buses do the same route every day - not to mention the delivery trucks that supply the lodge, tours, and pub at milford itself - so if they can do it you must be able to.
Be warned - in winter the road is slippery (frost on top of frost and black ice as well). The road maintenance crew keep it all in order and the hazards are well sign posted with grit laid down on the worst areas. Still - take it easy as you get closer to the tunnel - plus its a better way to take in the view.