after a few weeks playing with bitcoin, for me, the biggest problem are the FEES.
People keep spreading the wrong message that bitcoin fees are cheaper than fiat-c, and sometimes people says that bitcoin don't have fees.... BUT in fact, i never paid fees in fiat-c transactions, they are free in europe, and in bitcoin i am paying fees in every transaction... I am playing with some wallets, moving some bits from one to another and i pay fees that are bigger than the amount i am transferring! this is a huge NO for new users.
People here in europe are accustomed to free transactions and when they see the fees in bitcoin, they turn down bitcoin world. it is very sad

I am a bit disappointed too, if i am honest

You don't have to pay any fee if you send coins from A to B. It will/might take quite a bit longer to confirm compared to when you do add a custom fee. Miners have the power to accept which transactions they will include in their block, which mostly are the transactions with fee. Order your transactions, if a certain transaction of you has quite a bit priority, then add a fee. If it's not important, then do a very low fee, or no fee at all. If you're lucky it may confirm within a few blocks, but it can also take plenty of hours if not more than a day.