Like i said, convince me as a merchant to use your payment system while all my business expenses are in fiat currency.
So... what would convince you? What if you could pay 10% of your expenses using bitcoin, and it cost you 1% less if you used bitcoin?
There are lots of chicken-and-egg problems that bitcoin has to overcome to compete with the dollars or euros we're all using now; I see two paths to bitcoin's success:
Maybe there are enough ideologically motivated people to form a self-sustaining economy. If even 1% of people find the idea of bitcoin attractive and started using it for 1% of their transactions that would still be huge.
Or maybe one or more 'killer apps' for bitcoin will emerge, giving it a foothold in certain markets. Maybe it will never expand beyond those markets, or maybe it'll slowly grow beyond them because of lower cost and higher tech.
If you're not excited by the idea of being an early adopter for what could be a massively influential idea, then you should probably come back in three or four years and either tell us "Told you it'd never work!" or join what should, by then, be a much more stable and easier-to-use system.