I can't normally answer these sort of nerdy technological questions, but I can this one (whoo hoooo!)
We bought the zinwell digital receiver from Harvey Norman (knocked them down to $250 after haggling). The first box didn't work at all, and we took it back and changed it. Second one works fine. The quality control issues are to do with there being a dodgy bit (very technical eh) in the zinwell boxes that causes some channels to not be received properly, or even not at all. There is another fault that also means if your satellite dish is not totally 100% aligned to the optus D1 satellite (hey, i'm sounding genuinely experienced about this stuff - i even know the satellites name!) then it won't receive properly. however, from what i've read, if your box receives and displays the channels ok then the box is fine. We were aware about the possible problems with some zinwells (and Noel Leeming apparently has recalled them from what we were told at the shop) however OH bought it because (from his superior electronic knowledge) the zinwell is a better quality box than the Hills one - assuming you get one without the problem bit inside it.
As for the cheaper boxes on the internet, i've read that you can buy some which receive many more channels - esp if you have one of the new satellite dishes that have moveable LNBs (another techy term for the pointy bit that sticks out of the dish) capable of locating other satellites. Of course these other satellites no doubt transmit trash, korean shopping channels and the like.
Enough of this, better get back to my normal life....
In a nutshell though - we only got freeview box because there is virtually no terrestrial TV reception in our new house. It was either sky, freeview or nothing. I voted for nothing, OH voted for freeview as it's cheaper than sky in the long term (and neither of us want to watch the additional drivel thats on sky)