The obvious advantage is monetary. I spend $10 one time on the antenna and get to watch the 2010 Winter Olympics in HD. The downsides are the signal is really unreliable, at least in my location. It will go out quite easily and for no apparent reason. When it works, it does look really good though. When you consider how much you would have to pay for cable TV in a given year (and how much you watch it), it seems like a pretty good option. Netflix, the internet, and this antenna pretty much meet or exceed all of my watching needs. If you are into watching certain TV shows in real time as opposed to waiting for DVD, or are a big sports fan, this is definitely not for you. I am not the hugest fan of network TV. So keep that in mind :)
It is well worth a shot for $10 to see what channels you get. If it doesn't work, you can return it. If it does, you could be saving a considerable amount on your cable bill.