According to the biggest disadvantages of bitcoin is: 1. It's price is very volatility and decrease/increase at a very high pace.
2. If your BItcoin lose, then you cannot regain it. In simple words you lost it forever.
Your second point is not really a disadvantage, as the saying goes, it is not a bug it is a feature, bitcoin is that way by design, this is to avoid any third party being able to chargeback transactions, while this seems like a nice idea that allows a central authority to take your bitcoins without your permission, that is why satoshi decided against it.