The wedge has twist in its design but be aware that it does
not twist when struck for splitting.
The twist can help avoid getting caught in more fibrous woods but overall this twist doesn't provide any additional benefit that can't also be achieved with a any broader, highly tapered, diamond-shaped wedge.
The biggest benefit of this style -- and any broader, highly tapered, diamond-shaped wedge -- is greater outward force due to the much broader head.
From my experience, these type of wedges are not great for starting the splitting of bigger pieces but really come in handy when the "traditional" straight wedge goes in fairly deep but still hasn't completed the split (because there's not enough outward pressure being exerted by the narrower wedge).
I prefer these diamond wedges to the "twisties"
http://www.woodworkers.com/cgi-bin/FULLPRES.exe?PARTNUM=128-678&search=Wedge&smode=.
But I use mine only as a supplement when need to help the traditional narrow wedge. If you use these diamond wedges to start a split on something big, there's always the danger that the tiny point hits something hard before getting fully started, and the wedge then jumps back out at you.