Mildly annoyed now, mostly because of things related to my, up until now, awesome tidal wave weapon.
Turns out I have a vampire, so I promptly figured out who it was, drafted him and stationed him at an ideal location to try my new weapon.
Ordered everyone else inside (so I wouldn't repeat the mistake from last time where several dwarves drowned), and pulled the lever.
As the huge mass of water descended upon the vampire, I noticed two things:
1. Vampires do not drown.
2. More annoyingly, it seems that units aren't swept away, or even thrown off balance, by water. The only thing that happens is that they become less mobile. This seriously limits my enthusiasm for this as a weapon, since I imagined hordes of goblins being swept away by a gigantic flood. Sure, they'll probably still drown, but that won't be as cool...
As for my vampire, I think I'll drop a cave roof on his head, I need to do some landscaping anyway...
Edit: I thought the vampire would at least be annoyed by this. But nooo. "Dracula McVampire has been ecstatic lately. He was comforted by a lovely waterfall lately". Great, I made him happier.
Edit2: Operation "Crush the Vampire" is... somewhat successful. Yes, the vampire got crushed to a bloody pulp, all well so far. But then I went to mine out the remaining layer (I dropped two z-levels on his head), and for some reason there was another cave-in... killing two of my three miners. Ouch. No idea why that happened.