The road is in great condition and it is a lovely drive with gorgeous scenery.
Late July/early August is mid-winter so highly likely to have ice issues early morning, late afternoon - don't drive before 10am or after 5pm. There is a slight chance of snow on the road in which case don't drive until the road is cleared.
There are numerous tours by van and 4WD which travel Queenstown to Glenorchy and then beyond to Dart River and Paradise. If worried about driving take a tour - it really is the best way to truly experience the scenery.
Not the easiest of roads for one who had never driven on NZ roads. I don't imagine Florida to have anything like our narrow windy roads. ...
I personally think it's a really lovely road to drive - except when stuck behind extremely nervous drivers - 'stuck' is the key word there too! Being narrow, there aren't many places to safely pass - so keep an eye for cars behind, and pull over wherever safe to let them pass.
Usually there isn't too much traffic - though I have encountered a farmer moving his flock of sheep! (Slow right right down, but keep moving forward - the sheep will get out of your way).
While mostly it's a beautiful road, in great condition - it's not quite so at the moment - heavy rain over the weekend caused rockfalls and flooding - which blocked the road for 24hours.
You must also be cautious of ice throughout the day - check the QLDC website or Facebook page for their daily road report (posted about 7am through winter) and road condition updates.
Thank you WLnz and pineapplesensei. You have both been really informative. I gather it may be better for me not to drive this trip with the winter snow and rain. It sounds great for summer or spring though.
I actually only wanted to go to Glenorchy for some of the tours there but they don't all have pick up from Queenstown, mostly only pick up from Glenorchy. I am now looking at a company call Glenorchy Journeys that provides transfer from Queenstown to Glenorchy.
I drove along the road to Glenorchy just yesterday for the first time, in a small Mazda Demio rental.
Yes Queenstown has had a lot of rain lately, and I heard about the rockfall 2 days ago, but that didn't bother me. Was a great trip, no ice or snow on the road, the road is well gritted throughout the night I believe. However I have lived in NZ for 9 years so I am used to the roads (first time driving in an alpine environment though), but as long as you are a confident capable driver, this road isn't a difficult drive. Yeah sure there are some corners and hills, but NZ has a lot more difficult than that. You should have no problems, I would definitely do it if I were you, just take your time, and if you start to feel uneasy, turn around. There are plenty of spots to pull over and let other drivers pass.
Another update. Went along to Glenorchy again today, completely fine, road was gritted again over night, and was completely dry. Didn't come back until after dark, around 6-7pm, and people were still doing the speed limit of 100km/h along the road, suggesting the locals know the road is fine to use as normal until way later on into the night.