It's okay. Saradush and Watcher's Keep are particularly well-done, and are really quite interesting, and good. It can get a little tedious towards the end, though, since yes the combat can get a little cheesy, especially in the drow zones. And the Draconis fight is a chore, especially compared to Abazigal himself who is a pushover by comparison. I think it suffers some from APPEARING like a third full game in the series, when it's really just an expansion. If you treat it like an expansion instead of "Baldur's Gate 3" you'll enjoy it more.
One of the negatives is that the combat *has* to be cheesy, because D&D as a system wasn't designed for super-high-level stuff, it was designed to be balanced up to 20ish but not past that. Monsters get lots of attacks and will hit anyone and everyone very consistently unless they've got an AC of -15 or better, so it becomes sort of a race of who can heal the fastest, rather than the more strategy-oriented battles in BG1 and SoA.
Another of the negatives is that the party interactions are a LOT slimmer compared to SoA. Party members have things to say, but as a whole it's pretty bare, especially in the romance department. You've moved out of the area where most of the NPCs made their homes, so they're basically just tagging along for the ride... none of them have any quests in Tethyr. The game is also a lot shorter, but it's an expansion so that's really to be expected.
The positives are that it's pretty atmospheric, and the weapons are really neat, even if you have to do a bit of hunting to get them assembled. A genuinely useful club? AMAZING! It's also good to get closure on everything, like the epilogues and your destiny and even Saemon Havarian or the pantaloons.
Another of the bonuses is the increased level cap and the HLAs. They add a LOT to the game, and if you're running solo or with a small party, they can make a huge difference even while you're still in SoA. Mages actually being able to cast 9th level spells and druids not being useless are even better. They can unbalance (or rebalance) the classes a bit, though. Thieves and bards will reach level 40 at around 6.5 million XP, but they'll get lots of traps to set to make up for the "lost" XP. Mages won't get to level 40, but mages in D&D are powerful enough that it's not really a big deal... except that they only get extra spells, they don't get cool extra stuff like Use Any Item. Fighters, which traditionally have lots of trouble competing with casters at higher levels, can take as many Whirlwhinds as they want. Clerics are kind of in the same boat as mages, but they'll generally have enough 7th level spell slots to actually USE all of those neat bonus spells.
tl; dr: It's good, but it's not quite as good as SoA.