I see some sites have used it as currency, but they offer no seeable advantage off of amazon/other retailers, unless someone sees otherwise?
email on what is now the internet was first created in 1971, but most people in business didn't have an internet email address until 25 years later. how many years ago did you first learn of bitcoin? of those who know of bitcoin today, it has only been a matter of months since they first learned of it. in other words, rome wasn't built in a day so be so quick to judge.
amazon and other retailers won't start accepting bitcoin until it starts losing sales to others who do. there isn't much retail commerce occurring just yet using bitcoin -- but there certainly are niches either holding their own or growing nicely: http://en.bitcoin.it/wiki/Trade
what it sounds like the problem you are trying to get at is how to know that speculating by buying bitcoins is a good move. the problem is, by the time that the answer to that becomes more clear the exchange rate will have moved and then you'll be wondering the same question at a different entry point.
here's a useful guide though: http://bitcoinmedia.com/bulleted-advantages/