I have over 2 dozen hours in the game, and 2/3rds of the achievements. I have played through it twice. I intend to play at least until I get all the achievements. I am expecting 40 hrs.
I would call it a superior game. One of the few.
The story is good. Far better when you consider the between the lines interplay.
I am glad I bought it. If you like AVNs you will be too.
To see everything it will require multiple play throughs due to story forks and multiple endings. Time to complete depends on your definition of complete and play style. However, it was not meant to be a short game.
It is not buggy but needs polishing. Dialogue in English is a translation and needs work in places. The story is complete, The developers have promised an update which would flesh out some branches and add scenes. I hope they do.