They merciless killed Orik, the one non evil person in Thistletop. It's true that you can never prepare for what you PCs might do.
My party was pretty damn bloodthirsty. They'd encountered Orrik early, but failed to notice that he wasn't actually trying to kill them-- he was using disarm attacks in melee, and when the party retreated, he didn't impede them. I was playing him to have realized that he was in way over his head, and wanted out, but was smart enough to know that Nualia wouldn't let him simply quit. He was looking to the party as his way out.
Later, they encountered him asleep in his room. I figured that they would pounce on him, tie him up, and pump him for information-- and he'd be relieved, and genuinely grateful. But the barbarian slit the guy's throat while he slept! I've been referring to Orrik's death as a "murder" ever since.
Similar situation here, though he had even less of a chance. They encountered him in his room. He wasn't asleep, but the party Witch* quickly changed that. Next thing to happen was that the CG Sarenite Inquisitor slit his throat. :-\
He actually survived that though, but then the Desnan Cleric caved in his skull with a hammer.
* I'm starting to questiong the balance of that class, even if the character in question is rather optimized for Slumbering people (DC 19 at lvl. 1).
My party has just started the assault on Thistletop. I'm uncertain about how it'll go for them. Gogmurt pretty much told them where to go and to be careful with the bridge, but so far they've demonstrated an amazing ability to not listen to any NPC-given advice.
After the gnome passed over without incident (disguised as a goblin...) they didn't even bother checking if there was anything funny with the bridge. Unsurprisingly (to me) the trap triggered.
Only one character actually fell though, and he had a rather humorous way of avoiding the water:
He was the only one paranoid enough to suspect something. So he had a rope tied around himself with the other end attached to a crossbow bolt with a grappling hook. The moment the bridge fell he took the shot and swung to safety. xD
So far they've been fighting outside (and on top of!) the fortress. They'll be heading inside later this week.
Regarding Erylium and the catacombs:
The fight was more annoying then difficult, for my party. The shortage of ranged weapons and the fact that the opponent was mostly invisible made it rather irritating and drawn out. The biggest threat the party faced during the fight was when she summoned three riding dogs (the list I used wasn't quite up to date, I later realized). Them dogs hurt pretty bad.
Not counting familiars and animal companions and such, I think I've only ever had one character with cohorts of any sort.
My character was a Fire Genasi Cleric of Kossuth (the god of elemental fire in Forgotten Realms). Wherever he went he had a trio of mephits tailing him - a Fire Mephit, a Steam Mephit, and a Magma Mephit - all of whom were constantly praising his amazing awesomeness and generally making sure that anyone around were aware of what an extremely important and powerful person they were dealing with.
The rest of the party thought them a pest and a plague. xD