I think the biggest disadvantages of Bitcoin is what most often complaint by the other bitcoin enthusiast every time they do transaction and the confirmation always delayed. And then the other thing was bitcoin to other's is not a real currency instead it is still a digital currency which can be use only electronically, but can never be use physically in public place as payment. This was I think about it
You can use bitcoin debit card if you want to spend your bitcoins at physical places as it works same like the other bank cards and you don't have to pay any transaction fees if you make purchase using bitcoin debit card.