It could not be as good as the other BG games, because they had to put it in the middle of bg1 and bg2 and it was very restricted regarding the story, it is more like a "filler arc". A very small DLC could have been sufficient for that 1 or 2 more levels, but I enjoyed it.
It is an important arc though, because Shadows of Amn's intro tells you that you were forced to leave Baldur's Gate under some very dark circumstances after the authorities of Baldur's Gate figured out that you are a Bhaalspawn. Also the expansion does a good job of showing how you ended up with Imoen, Khalid, Jaheira, Minsc and Dynaheir even if you did not have them with you when you defeated Sarevok, and how Viconia recognizes you in Shadows of Amn even if you never met her in BG1.
And the expansion ties up a loose end from Icewind Dale.
