Bitcoin has been impressive in a lot of ways since it's beginning but the one thing that blew me out the most was the ideology. A foolproof peer to peer online transaction system based on blockchain technology was just a beautiful set of works executed and implemented by Satoshi and no wonder it has already made its mark in every field it is being used in.
The thing that impressed me in bitcoin is its uses. Bitcoin has maby uses and it would depend to you on how you would used it. In addition to that, the first that impress me is being decentralized of bitcoin and we all know that no can control it. Lastly, the high price of bitcoin is also reason why Im totally impressed.