Well one that i can think of is that it is still not perfectly anonymous. Personally i'd like to see bitcoin evolve into the future into something like XMR with essentially in built coin mixing. This is probably not necessary but rather an add on.

Another thing is that, fees are often high.

Also, blocks are 10 minutes on average in between so that means you're probably not going to be able to get stuff irl instantaneously without the merchant having to trust you.