I went through VIE about a year ago flying Austrian from NYC-VIE-DEL.
I had about 2 hours in transit and as a star gold was able to access both Austrian airlines lounges (one downstairs, one upstairs - can't remember the differentiation but both allowed star gold).
The upstairs lounge had showers - nothing flash - but very welcome for me. Both lounges had lite cheese/meat selections and friendly staff (no real meals). The only complaint I would have (and this may have changed) is that the upstairs lounge where I had my shower allowed people to smoke throughout the lounge.
The lounges are in the VIE long haul international terminal which is a small circle with about 8 gates off it. It can get crowded when they are boarding one or two longhauls so the lounge access was welcome. Staff were friendly and recognised my Star gold status no problems.
As far as I could tell there were no other star alliance lounges.