Confirmation time
That is the problem with majority of us, but I think it will be resolved in future by the core development team, apart from that I don't see any problem with bitcoin.
Visits the LN site, and learning this. maybe Lightning network will become the answer to this problem, in the future lightning network is a solution for some big or most common problem on bitcoin. I'm very excited about this project. without block confirmation, the transaction will automatic confirmed and upgrade block size.