Yes there are several disadvantages as well and as well all know comparison = similarity + dissimilarity. On this note I would like to point out some relevant points regarding this matter:

1. Volatility of price of bitcoin is there which makes it a prime target for traders. Bad news for stores/shops
2. Payment Gateways integration is low for bitcoin with respect to fiat currency.
3. Payment Availability in bitcoin is also low. Not many people get paid in bitcoin for offering their service (I am talking in general which means outside this forum)
4. Acceptance and Popularity - bitcoin needs more acceptance throughout the world, that does not mean the US/UK - the rest of the world is also there.
5. Irreversibility of transaction - though I consider it as the least because it is a fault of the user to mis-click and not system. However we are all human and we tend to make mistakes.

Edit: I did remove one about which I am also not very confident as a disadvatage but is rather a misconception.