This is a HD set top box. Cheapest units I have seen are around $99, plus shipping. Advantage here is no shipping costs - pickup at any Hardly Normal store and you can return if it's not suitable again no shipping or hassle.
With Set Top boxes you really need to try as te quality varies greatly with different reception areas.
The HD unit enables you to get the new broadcasts by Channel 7 and now 10 (Nine - still ONLY the one), which has different content. SD boxes will not give you these channels
You can also get ABC 2 and SBS (also available with the cheaper SD)
While a standard TV receives the new broadcasts, with HD boxes you just don't get the extra definition. (Whereas with a SD box you dont get anything)
HD boxes prolongs the life of your old TV and video recorders, in the past these were around the $300 mark, now they are becoming affordable.
The HD boxes will also work with earlier Plasmas and LCD TV's that were sold without HD or SD tuners again prolonging their useful life
Voting up for the description alone … now I can put all that techy stuff into normal speak for the parents :-)