It has created a new way to send money across the world with very small fees. This may not be such a big deal for Americans, but in some countries being able to send money to/from abroad when they can't access a bank account or Paypal account is a big big thing.
It does have it's weaknesses though. The first is that you need a good knowledge of security to successfully manage your own bitcoin stored offline. For example how intuitive is it that spending from the same address twice is a potential security hole? Or that your RNG isn't good enough.
Otherwise you store it online, but that has a lot of risk as we have seen with so many successful attacks in myriad different ways.
The other problem is no one really trades in units of Bitcoin. The value of something is in a fiat currency e.g. USD which then needs to be converted to Bitcoin, and so when your Bitcoin crashes to 50% of what it was worth yesterday, it becomes high risk just to hold it. It has no intrinsic worth.