On the top of my head, here's a few.

• Liquidity: As liquidity is low, big market orders are expected to significantly move the price of bitcoin or cryptocurrencies in general. This is something that will be "fixed" as more money goes into the bitcoin markets.
• UI/UX/user-friendliness: Bitcoin might be easy enough to use for most of us here, but it's definitely not for non-tech savvy people(e.g. our grandparents). Especially with the handling of private keys; I don't think we can expect true global adoption if people needs to backup their recovery seed on pieces of paper.
• Misinformation/Misunderstandings: There are so much misinformation spreading about bitcoin. Namely, "bitcoin is not scarce, people can create forks", "bitcoin is only used for drugs", and many more. There's so much misunderstandings of people in social media and on television; and what's worse, is that they're spreading their misinformation! Causing a sort of domino effect on people's impressions of bitcoin.