My heart is divided by Kingdom Hearts 2 (Naminé <3) and Birth by Sleep. But the topic is about BbS so all I need to say is that's a must play for every KH fan out there.
The characters are awesome and very different, I can't choose my favorite and everyone has a decent and relevant story and motivation. You will finish the game 3 times and will not be bored in a single play.
After playing It I've be thinking If the series would not be more popular if Ventus, Terra and Aqua are the original protagonists...
Don't kill me, I know Sora is important but after BbS his story sounds more like an spin-off of the events that occurs in the past.
If you can wait, december will bring the remake in HD. (And I will play again)