In reply to Dori79:
Best time is from end June/beginning of July to September. Usually, but not always, crossing the snowfield is ok without crampons, but this is dependent on the seasons snowfall and specific conditions. Usually reliable information is to be had at the hut.
Shortest descent still is down to the cable car, around to Hunerscharte, and down the easy ferata back to Südwandhütte.