g'day aichi,
If i have read your question correctly you are wanting to travel top Queenstown and back in one day.
It will take you straight driving around 6 hours and this does not take into account for the holiday traffic you will experience, there is a lot to see on that road and yes there is one area called The Lindis Pass that area can be quite windy and they have cautionary signs up.
Other than that it is a beautiful drive and is worth taking your time the roads are not designed for excessive speeds so be prepared to enjoy the scenery if you want to go to Queenstown and just drive then my suggestion is get a Bus there and that way you can see the views also when you are in Queenstown there is so much to see that you could easily spend a full day and not see it all.
New Zealand may be a small Island but there is so much to see and do here is a link to the distance calculator it will help u decided what distances u are covering
http://www.accommodationz.co.nz/distances2.html#another tool is this one it says 7hrs to Queenstown so it all depends on your road conditions
http://www.newzealand.com/travel/getting-t...tances-home.cfmI hope this has given you some help an insight to the trip you are planning
Cheers Stewart