I think the biggest disadvantages of bitcoin right now is that there's not many merchant who accept bitcoin as a payment method. The other disadvantages is the transaction speed, the confirmation can take a lot of time sometimes.
how can you say that this is the disadvantage of bitcoin. i think bitcoin is still not so much mature it still need a good time to become more famous. i think it will still take some time when merchants will accept bitcoin and will do trade in bitcoin. the transaction problem will also be solved very soon.
the absence of many merchants who accept bitcoin as some countries do not accept bitcoin as legal payment so they did not dare to do it. bitcoin transactions can not be canceled even though is still 0 confirmation it will definitely be sent