Less than forty chapters have been released, which is a pretty small number for fantasy webtoons. That said, my current impression of the story is fantastic.
He is overpowered, but not too much. The manhwaga makes it a point to say he is not in fact a "genius", but instead very well-equipped with decades of experience and knowledge. And even that experience and knowledge was gained in a rather sensible way during his unimpressive first life (at least in comparison to other stories of this genre).
There also haven't been any needlessly repetitive displays of genius, like the kind the more obnoxious reincarnation/time travel stories tend to shove in your face.
Further, while I am curious about his family, his relationship with his master is heart-warming, and it helps to shape both him and his master as empathetic characters.
The female characterization, from what little I've seen so far, has also been pretty great. There haven't been any ridiculous body proportions, or sexist caricaturizations of personality/skill. (Though, obviously, there are signs of Gender Roles, but that's to-be-expected.)
To top it off, the main character is just likable. He's level-headed, caring, determined, and has a decent sense of humor. He's not cruel, perverted, idiotic, arrogant, or particularly prideful, but neither is he lacking in human flaws.
It's still early in the game, but I'm liking what I'm seeing so far.