I have been to Vienna a couple of times before and will be going again this December (Christmas Market tour)
Vienna is a great city any time of the year but keep in mind that the level of activity drops after about 10 pm at night. This is unlike Paris where you have lots of foot traffic well into the small hours of the morning.
This time I am staying at the Hilton (I am kind of loyal to Hilton and Hyatt).
http://www3.hilton.com/en/hotels/aus...WTW/index.html
this is the hotel. it is closer to the city center and the cost is around 200 US$
Last time I stayed at a great B&W hotel very close to the market and a couple of blocks from the opera. it was simple and very nice. They recently remodeled the place and the price is higher.
http://www.hotel-beethoven.at/home.php?lang=en
I think you could certainly enjoy a few hours in Vienna. You could wake up earlier and go for a walk and enjoy the city as it wakes up.
I am more of a morning person and love to wake up early and just go out for a walk; find some coffee and enjoy the quiet morning.