least favorite thing bitcoin is the lack of marketing and public awareness it. due to with it is still believed by many be a geek thing, simple or people who are not in the web world much don't want to get into bitcoin world.
That's true majority of people are not aware about the bitcoins as it lacks promotion on international level and if it get good recognition then it can reach to many people and it will also attract them towards it.
This is something that can change in the future, as more and more projects surrounding Bitcoin getting global recognition.
Plus there is also a form of promotion that is not done through advertising, but just through the adoption of Bitcoin by major companies.
More and more people see the Bitcoin logo popping up when they pay for something, stuff like that really helps people becoming aware of Bitcoin.