Overall, I can see many similarities between this and Saiunkoku Monogatari. I wonder, though, whether this is because all the reverse harem stories are really all the same. Don't get me wrong, I think Hanasakeru Seishounen has many great things. It's just there aren't enough reverse harem animes out there, so every time a new one comes out, you just can't help to compare with others.
Hanasakeru Seishounen is a very good story. In my opinion, romance and politics is almost always an interesting mix. Here we high level politics, high level inter-corporation play all mixed up with a strange romance. On top of that, all characters are really well developed. Despite many seem somewhat unrealistic (well, maybe it's just that I don't know enough about how extremely rich people live), you still get a sense of connection to the characters.
As for the way it ended, generally, I'm not a big fan of nearly perfect endings. But in this case, I have to say, after watching what every character has to go through, I think they've earned it.
Final scoreboard:
Drama: 92 (All about drama)
Comedy: 86 (Not bad for what it had)
Action: 82 (Somewhat corny, but not bad)
Art/Animation: 80 (Looks somewhat...unusual)
Sound/Music: 80 (Nothing special)
Character: 89 (Very well developed)
Plot: 87 (Twists and turns)
Ending: 90 (Tied up all loose ends)
Re-watch value: 30 (Wouldn't be nearly as interesting)
Overall: 88 - Well made reverse harem
Recommendation: Being a season and a half long (39 episodes), I don't think people with little patience would be able to even get through the first half. But if you do manage to get through the first half, you'll find this is a plenty interesting story.