I really don't see the point of these cards. Only worthwhile if you are betting really large amounts and want the cash out asap IMO.
I think it's a brilliant idea. 60+% of punters are probably living week to week, if you are down at the pub on a saturday arvo and back a winner and get $500 you want to shout your mates and get a feed instead of waiting 3-5 days from the Saturday to get it in your account. It's lost its ZING by then. There's also the odd occasion where you accidently put the rent money on a good thing that gets done. You back the winner in the next, grab your money from your card and the Mrs is none the wiser!