All of these have been commented on before.

  • Variable block size. If adoption grows it will cause the blockchain to grow really quickly. Over time, you'll end up with the same centralization problem that Bitcoin would have had if it increased the block size.
  • Not a criticism of Monero itself, but I dislike the community's lack of interest in sound economic principles (aka Austrian economics). That will affect Monero's future monetary policy.
  • The tail emission. Yes, its disinflationary over time. However due to the second problem, I can easily see the tail emission being increased. I think that its better to have a totally fixed supply and no tail emission so that the temptation isn't there.

Reasonable concerns :)