Ideally new era of currency should be perfect and no disadvantages, the most important feature is the speed, security, low cost and could be accepted for all transactions (online and offline), I see bitcoin it's not there yet.
I agree but still bit coin is improving aggressively, it has overshadowed paypal which was a good source of transferring money, now bit coin is here. You can purchase online with bit coin, you can even buy property in some advanced countries. It is fully spread online and in future it will be accepted offline too as a confirmed currency.