When we had that cold snap a couple of weeks ago it was snowing on the mountain, but it was only a couple of cm and was gone by mid-morning. Last winter I only remember one day when there was full-on snow a couple of feet deep that lasted for a couple of days.
It just depends really. Mostly in winter it is cold and wet but there are good days. I was at Camel's Hump last Sunday morning taking photos and it was beautiful - sunny and dry. Would have definitely climbed if I'd had my gear (and I'm a wimp on cold rock).
It helps if you live nearby and can see what the weather's doing, rather than doing the trip from Melbourne with your fingers crossed... The best you can do is look at local weather forecasts before you leave, and try your luck. There's plenty of other stuff to do in the region if you get there and the climbing's looking too miserable...