Try the "Similar Threads" section, which you can find by scrolling to the bottom of your thread. This saddle comes up for discussion quite a bit, and there's lots of older threads about it. The short version? Worth considering, but don't overpay for it, especially considering you can often find the saddle it's based on (the Passier Grand Gilbert) for very similar prices. However, if you have a very wide horse, the Vienna may merit some attention since it's built on a U-shaped hoop tree.
I have one and I like it. I have a medium tree for my somewhat wide QH. He does have a wither but he also has a very well sprung rib cage which sort of makes him flat across the back. He is not "draft" wide though.
As soon as I put it on him I noticed he was much more free through the shoulder.
I'm currently using a Thornhill Germania saddle on him and I like it a lot too.
Anyway I bought the Vienna II new about 2 years ago for just about $1000.00 to give you an idea of price. If the one you're looking at fits and is in good shape it's a pretty good price. Not as nice as a high end saddle but a decent value for the money.