Thanks for giving people the opportunity for input, Rodney!
Firstly, I'd like to endorse all the previous comments by
Rechan and
Mustrum, which express many of my thoughts but with greater clarity of expression than I could muster.
I've DM'd Keep on the Shadowfell and Thunderspire, and I'd like to make a few comments based on my experiences there.
1. Too much fighting, not enough talking
As written, KotS seemed to revolve almost entirely around fighting at every opportunity, it didn't have any opportunities written in the adventure for negotiation, for Kalarel to have visitors (or adventurers pretending to be visitors).
As a related issue, I don't remember exploitable tensions between dungeon denizens. Sunken Citadel (all those years ago) had the ongoing turf war between kobolds and goblins which gave rich roleplaying opportunities. KotS could have been dramatically improved by having some motivations for relationships between kobolds, goblins and hobgoblins, including reasons why they might turn on one another.
Sir Kalarel could have been a really interesting character in KotS, but I felt his story was a bit confusing (and, in fact, the whole temple thing with the skeletons where he was seemed a poor fit together, not terribly cohesive?)
2. Jack-in-a-baddie
Both KotS and Thunderspire had a final baddy who pops up at the last moment. We've not seem him before, we've barely heard of him before, nobody has any reason to hate him. He has no reason for knowing anything much about them, he doesn't really know their capabilities and strategies as he would if he had a previous encounter of some kind.
Also, there isn't really much roleplaying opportunity here (unless they can get him soliloquising, (nods to The Incredibles))
3. Linearity
KotS would have been improved IMO if there had been some options included such as a Hobgoblin attack on winterhaven in reprisal after successful adventurer attacks into the upper levels.
The side adventure to the excavation site could have been really interesting, but wasn't tied into the adventure well enough. It would have been good if the adventurers choice of which order to follow up clues had a real impact - what if the PCs had got the maguffin from the crater first, so that Kalarel has to negotiate with them? What if they left the crater to last and so find evidence that their friend has been taken off by slavers one way, and an artifact has gone down into the dungeons?
I like to see adventures which give the PCs the opportunity to make meaningful choices with consequences.
4. Surprises
I think a great adventure contains some mysteries and some real surprises/shocks for the PCs (and the players). Of Sound Mind was particularly good in this respect, as anyone who visited the farm will know

.
Cheers