I think the most impresses about bitcoin is anonymous, as we know that the current privacy requirement is very important and bitcoin has understood it so it makes me very happy and likes the anonymous features.
Bitcoin impressed me much in all terms, its price, volatility, decentralized and popularity. After a year, it makes me amazed in its price rapidly do up. In past 4 months, bitcoin price reaches 18000$ and I think the bitcoin price will reach 20000$ in 2018.