Frankly if you loved the original you will love this game. There's not that much more to be said about it, but here I go anyways.

First and foremost: DO NOT PLAY THIS GAME WITHOUT HAVING PLAYED EVERY ROUTE OF HATOFUL BOYFRIEND, INCLUDING BBL. I can not stress this enough. Anyone who isn't familiar with the real plot of the original and only remembers "bird dating sim" is going to be incredibly confused and also bombarded with spoilers.

Visuals:
Obviously not the main draw, but HS actually puts a heavier focus on the art than before. Half of the new characters actually have their sprites drawn out, and while it is limited to bonus scenes all the main 8 have human portraits. Nageki's smile in his human portrait will never cease to shatter my tiny little heart. The story books and all the art specific to the last two chapters is actually really beautiful, surprisingly. I wish the gallery included things like backgrounds and the field in the ending.
Sound:
While it's important to note the soundtrack is all royalty free music, it is amazingly good royalty free music. I'm currently on a quest to track down all the remaining downloads for these songs because they are rad and I could listen to them forever. Sound effects work the same as the last game.
Technical/Gameplay:
Same slightly awkward delays and such when making choices as the last game, still not too noticeable. Instead of romantic routes the game is now divided into four linear chapters without romance and plenty of bonus scenarios. I think this new, linear format is much better suited to the story, as it ensures people will actually play through to the true ending this time instead of dismissing the experience solely as a gag game. It's shorter, but I think the length is fair enough for the price. I love all the bonus scenarios and radio Q&As too. Some of the choices rely on prior knowledge, one of which I found particularly clever.
Also oops we got a Japanese-only CD spoiler.
Characters:
Just as good as last time. Honestly I don't feel the need to delve into this too much, if not just because of spoilers, but all the charm mixed with bird-induced depression is still here. The new characters feel like natural additions to the story too and are just as fun and/or tragic as last time.
Writing:
That charming, utterly absurd sense of humor is still there. The translator, bless their poor soul, had so many puns and wordplay-filled moments to work with and they did a great job regardless. Sometimes the translator addresses these issues in a cheeky, direct manner that works fine within the setting. The main plot in the last two chapters has a lot of ethereal fairy-tale like elements to it, and the writing style really helps capture that mood. I love it. I also noticed less typos this time around, which I'm grateful for.
Plot:
I can't believe I'm crying over birds again. Once again this game starts as a gag game (in the first two chapters) but actually provides excellent foreshadowing for a shockingly well-written thriller. This takes place in a weird kind of alternate continuity from the last game where a lot of the background that's brought to light in BBL happened, but certain moments and the overall BBL plot did not. It actually gives further development to several of the characters, and I can not even believe that it's making me sympathetic towards Shuu of all people (birds, rather). The finale is very heartwarming and melts my little bird-loving soul.

If you finished the original and liked it at all, this is a must-play. If you only played part of the original, go back and finish it and then buy this game.

Frankly if you loved the original you will love this game. There's not that much more to be said about it, but here I go anyways. First and foremost: DO NOT PLAY THIS GAME WITHOUT HAVING PLAYED EVERY ROUTE OF HATOFUL BOYFRIEND, INCLUDING BBL. I can not stress this enough. Anyone who isn't familiar with the real plot of the original and only remembers "bird dating sim" is going to be incredibly confused and also bombarded with spoilers. Visuals: Obviously not the main draw, but HS actually puts a heavier focus on the art than before. Half of the new characters actually have their sprites drawn out, and while it is limited to bonus scenes all the main 8 have human portraits. Nageki's smile in his human portrait will never cease to shatter my tiny little heart. The story books and all the art specific to the last two chapters is actually really beautiful, surprisingly. I wish the gallery included things like backgrounds and the field in the ending. Sound: While it's important to note the soundtrack is all royalty free music, it is amazingly good royalty free music. I'm currently on a quest to track down all the remaining downloads for these songs because they are rad and I could listen to them forever. Sound effects work the same as the last game. Technical/Gameplay: Same slightly awkward delays and such when making choices as the last game, still not too noticeable. Instead of romantic routes the game is now divided into four linear chapters without romance and plenty of bonus scenarios. I think this new, linear format is much better suited to the story, as it ensures people will actually play through to the true ending this time instead of dismissing the experience solely as a gag game. It's shorter, but I think the length is fair enough for the price. I love all the bonus scenarios and radio Q&As too. Some of the choices rely on prior knowledge, one of which I found particularly clever. Also oops we got a Japanese-only CD spoiler. Characters: Just as good as last time. Honestly I don't feel the need to delve into this too much, if not just because of spoilers, but all the charm mixed with bird-induced depression is still here. The new characters feel like natural additions to the story too and are just as fun and/or tragic as last time. Writing: That charming, utterly absurd sense of humor is still there. The translator, bless their poor soul, had so many puns and wordplay-filled moments to work with and they did a great job regardless. Sometimes the translator addresses these issues in a cheeky, direct manner that works fine within the setting. The main plot in the last two chapters has a lot of ethereal fairy-tale like elements to it, and the writing style really helps capture that mood. I love it. I also noticed less typos this time around, which I'm grateful for. Plot: I can't believe I'm crying over birds again. Once again this game starts as a gag game (in the first two chapters) but actually provides excellent foreshadowing for a shockingly well-written thriller. This takes place in a weird kind of alternate continuity from the last game where a lot of the background that's brought to light in BBL happened, but certain moments and the overall BBL plot did not. It actually gives further development to several of the characters, and I can not even believe that it's making me sympathetic towards Shuu of all people (birds, rather). The finale is very heartwarming and melts my little bird-loving soul. If you finished the original and liked it at all, this is a must-play. If you only played part of the original, go back and finish it and then buy this game.