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.
Pretty much this. Before SoD there was text. Did we need this game? No. For something that wasn't needed though, it really delivered. I think that was the surprise, having SoD to begin with.
Beamdog did a good job with the EE. Interesting characters they added although they are all way more present than most other companions, which some people didn't like as much. I enjoyed them a lot and the Friendly Arm Inn is looking really good with every single companion together.
SoD was that linear piece that was missing in between BG1&2. They tried out a few new things I liked but overall it was not quite as good as the original games. Due to linearity.
Dragonspear feels and plays quite literally like an actual bridge between the games, linear and somehow suspended between the great story arches.
Combat is the combat you would expect and a natural progression from the end of Baldur's Gate. It goes too far when levels are retained after what Irenicus did to the player character though. Just roleplay it and start lower.
The art is great, looks, sounds and feels just like Baldur's Gate or an infinity game, cause it is.
However! The pathfinding. Was not. Made. For. A crowded. Baldur's Gate