I stayed in Avis a few years ago, and I think everyone should be aware of the fact that it is more of a student hostel than a hotel. More than half of the people staying there are foreign students, and no one really considers it to be a true hotel.

The rooms were very clean, and the price was so low that one simply cannot complain about uncomfortable beds when they are hardly paying anything to stay there.

I stayed at the Guesthouse Avis(same building as hotel Avis but cheaper rooms with shared bathrooms on each floor) for 5 nights in September.
I was disappointed but for 23 euros a nite(single room) I can't complain as that is extremely cheap for Vienna.
The staff was friendly,the breakfast was pretty basic(buns,jam and coffee). My bed was clean(but not very comfortable) and the walls of the room were somewhat dirty.
And at night it was very loud, constant shouting and slamming of doors.
The room had no tv or radio or even a clock which was a bit surprising.
I would stay here again though just because its so cheap and its not like I actually spent alot of time in the room anyway.

I had stayed in this hotel several times in the past so that is why I booked it again. Although the beds were clean, the walls were filthy, the beds were cot size and uncomfortable the room was unbearable hot and small-a single room made into a double, the curtains did not close around the windows. It was noisy all night long. It is also the youth hostel. The bathroom was really grubby and the final straw was when the toilet seat fell off! The picture on the website does NOT resemble the rooms at all. I would not recommend this hotel. It looked more like a prison. We booked for three nights and left after one. The only good thing I can say is that the staff were friendly and helpful and the cleaning staff worked really hard with what little they had