Well, introductory adventures have a tendency to look very similar, so KotS has a handicap right from the start. KotS had the better poster maps, though.
In Thunderspire I mostly liked the first two dungeon locations. The third is a bit too weird for my tastes and the last one is too short and imho too uninspired to work well as the adventure's climax. It's also not really linked well to the plot.
I probably won't get H3, though. From what I've seen so far, it's too over the top for my taste. My opinion may change when more info is released and when I've read a review or two.