This is a good adventure, well written with an interesting plot, good artwork, well statted NPS's and monsters and an interesting finale.
It fits the FR well, reacting to Lolth's silence but not mirroring anything that happens in the six novels series written specifically about it.
Problems?
It is a bit of a dungeon crawl, being set as it is in the Underdark dealing with drow, demons and other inhabitants of the dark. It sometimes seems a little difficult to speak to anything, as everything appears as evil. This could be very hard on a party with a gung ho paladin or priest. LG players will need sharp swords and strong magic.
It suggests the party can be drow, but then does not really follow that up later. Every encounter is written as if it is a surface party coming down, rather than a drow party working for its own means.
The end is too hard. The DM will have to modify the last encounter in my opinion, or a total party kill is on the cards. Horrid Wiltings anyone?
The equipment and items you find are a little boring to. Not enough unique items or just different ones. Lots of Rings of Protection +1 or +2, minor bracers of armour, rapiers +1 that kind of thing. Little we found whilst adventuring caught my eye. I felt some more specific underdarky kit would have been nice. Some signature items. An elven sword stolen years ago from Myth Drannor or some Duergar armour with a (grumpy) personality. That kind of thing.
These problems are surmountable, and if you can get your head past the fact that it is a long meatgrinder of an adventure then it is very enjoyable. Some good set pieces and a clever overall story.
I would just make sure any party who play it are a little stealthy and capable of at least pretending to be less than herioic, as without disguises or very clever play they will end up fighting everything and roleplaying encounters could be thin on the ground.
An Elven Holy Liberator of Corellon Lerathian would not be a good choice to play!
I enjoyed playing it for the most part, just wish after reading it afterwords we had played different characters and started with a different attitude.
Good work in general WotC, let's have another one. Perhaps with a few less drow this time?