I have two groups that have run through book 1 and are starting book 2. The interesting thing about running the two separate campaigns is that I get to see just how subjective the 'toughness' of the fights are.
Early on, it's pretty much a toss up, 'cause it's so easy to damage low level characters - that said, I'd say the major fights in book one were:
For my Friday Group: the Ogre in the hedge at Hockton Barrow - It was just a roll of the dice, but a crit with a scythe is x4 damage and caused the first player death in one group.
The columbe mansion was tough in places mostly because of a series of failed turning rolls - but it wasn't severely life threatening - although the same rogue got hit with the cocatrice's nastiness, and had to be hauled to Saragost in a stolen cart. One of the most fun fights ws the hooka. Come on, how many DMs get to bash on their PCs with a hooka? both groups failed to find that trap, and got wailed on.
Neither of these encounters were a problem for the other group... However I did get a TPK in my Thursday group from the ambush in Saragost - completely due to a series of poor choices, and really bad die rolls. Again, the other group had no problem here.
After they got their weapons, I"m having to alter the monsters - usually I"m just giving them max hit points instead of average. The players who've settled on holy damage (most of them) do prety serious damage almost all the time.
In hindsight, the thing I'd change in the first book doesn't have to do with fighting, but with divination... The deck of cards in the columbe mansion, and the orb in the temple of Karad both have divination abilities. That, combined with the cleric's spells are giving these characters a ton of divination attempts. In one day, one of my parties used divination 5 times.... now I'm getting very good at precise but confusing answers, but It's still a bit excessive. I'd rather they didn't have the divination from the items.
js