It sounds like an interesting idea, but it has a few drawbacks I think. A quick example: If you wanted to move to another city, you may not want to keep every piece of furniture and instead "sell" it. You could just gift them to your neighbors or the next person moving in but you paid for it with vouchers and you don't want to waste the hours worked after all. How would you get rid of the furniture while still keeping its value? With a currency it's trivial - just sell it. But you can't really do this with vouchers, since they can't be transfered by design. You could perhaps trade it, but what if no one has anything you need?

And that's ignoring the glaring privacy issues of a centralised, personalised labor voucher system. Sure, it prevents fraud but it also allows the government a lot of insight into your life.