dark void is only 30 AUD. should i bother?

Not really.

Get Dark Void Zero instead. It's $5.

I have seen it for less than that locally (Australia as well) - $25 and no, I wasn't tempted to buy it.  The reviews paint a rather bland picture - a 59 average isn't confidence inspiring: 
 Dark Void (ps3) reviews at Metacritic.com

Nope, you shouldn't..

I agree with Oldschool, and plus there's much better games coming out or already out you could waste money on, and I'm sure with all the games coming out 1 of them will take your fancy.

Dark Void Zero is a much better game overall.

 
Yeah I would hold on to that money and save it up for a new release game... but if you feel the urge to try it out you can always rent it. But I agree with everyone else, Dark Void Zero is a better game.

Dark Void Zero is a DSi game, just in case the OP wasn't familiar with it.

I got it free with a magazine several months ago. Never bothered playing it...

" @oldschool:  It's also on Steam. "

If it's $30 now, I would expect it to go even lower. I myself wouldn't buy that game unless it was around the $10 mark. 
 
And then it would sit in my games collection unplayed, like so many other cheap titles.