The possible impact of the bitcoin in the economy for a country will be good because the people will find faster way of transacting money and transferring money from one point to another. The flow of money will become so much faster and it will make the economy of the country much healthier than before and i think that is the impact of bitcoin and there is nothing to worry about the negative impact because they can be fixed with an ease.
The speed of a bitcoin transaction definitely has not been a strong point for the currency at all points and even though its being improved over time, I think it's not a strong point to build support for the currency on. Instead, support will come more from the fact that bitcoin can be treated as an asset and the fact that it is an anonymous currency. People enjoy being able to spend their money with a certain level of protection -- they get that protection from using bitcoin.