Put it this way, I'm constantly visiting the Pokémon Center.
Relatively, the game does feel a bit more difficult compared to the past generations. The wild Pokémon specifically seems to have gotten more challenging, especially compared to DPPt. Something I've actually noticed, and I don't know if this is just happening for me alone, but Critical Hits seem to occur a lot more often than before, which is one of the reasons why I'm always heading back to visit the lovely Nurse Joy.
Lenora, the second gym leader, also seemed a little bit challenging. I beat her on my first try, but she managed to take down two of my Pokémon early in the battle with her last Pokémon.
Other than that, I wouldn't say I've gotten that far into the story line (I've only recently arrived in Castelia City), but there are more trainers around compared to other points in the game when this far. I don't necessarily consider this a difficulty in the game though, but more of a chance to boost up my Pokémon's level more.