First big limitation of Bitcoin is surely high transaction time, but it is not the worst problem. Second big problem is adoption rate and issues about regulation. Governments simply are not ready to adopt Bitcoin in a regular economic system and the explanation is in the decentralization. Without any central institution that have full control of Bitcoins, government can\'t control fluctuation of Bitcoins value and the price as well. Another big limitation of Bitcoin is limitation of supply. There are finite number of Bitcoin and that is the reason why people are comparing Bitcoin to the gold. The value of Bitcoin is rising all the time, which can create some difficulties to actually buy something with Bitcoin.
For Bitcoin, which is developed as idea to became globally everyday payment method it\'s very important to be globally adopted and every negative statement by government is influencing inversely by decreasing the rate of adoption. Bitcoin has became everyday word in peoples language and we can surely said that Bitcoin is completely adopted by innovators and early adopters which are mostly people with good technologically knowledge. Much larger portion of global population is conservative one and they are just now accepting Bitcoin due to lack of knowledge or lack of thrust in technology.
The main problem is transaction time and block time that are high, and the reason can be the amount of computational power behind the network and all the miners within it. People will not use Bitcoin as a payment method if the payment process will last for more than a few hours. The protocol need to be upgraded. When we are talking about computational power, we can be sure that it will decrease once when all the Bitcoin are mined. There are some suggestions that are including small fees per transaction to the miners, so they can continue making a profit from the mining.