I can't believe no one mentioned the most objective advantage of bitcoin: I can send money around the world without paying anything.
It may not be that useful to the average consumer, but it is the first currency that allows this. For example, I am an european and I really like dealextreme.com because they offer free shipping and they sell cheap stuff. I would really like to pay them with bitcoins because I lose a lot of money with the EUR/USD conversion.
Also, bitcoin is not anonymous by design. It allows for a certain degree of privacy and it can be sort of anonymous, but you must use other tools for that. I agree with most of what faustianover said. Bitcoin does not have one simple great advantage for consumers. It is technologically rather interesting and it offers some interesting features that some people want. However most consumers simply don't find these attractive enough to justify the change. At least right now.
So how do you change this? The sending money worldwide without worrying about conversion (Well, assuming bitcoin prices stabilize) is a good thing. It's also the only one I'm hearing.
A lot of talk about the upsides to Bitcoin requires Bitcoin be in common use. Sending money just to friends, not paying credit card fees, or having to worry about PayPal. To see these as superior to the alternatives, the community needs to sell the concept of Bitcoin. It's an uphill struggle.
It feels like one of the main reasons people get involved with BTC is as an investment vehicle- Either to start mining, or to play the 'buy low sell high' game (I guess scammers could fall under this too, get money quick schemes). This doesn't support BTC in the long run- A major drop in the exchange rate and people in this category would leave. Already I get the feel that most of the forks are in the same vein- Longing for the days when BTC was much easier to mine, before the peak in prices over the summer.
From a layperson view, I'd think getting more Average Joe's into BTC would help support the stability of the currency. It would certainly help get more established merchants to accept it, and help ensure its longevity. I just don't see an effort made to legitimately make Bitcoin attractive.