I can't stand locked threads (and I'm speaking of webboards in general, not just here).
Most of the time I read a locked thread, it's because I don't see that's it's locked, and I waste my time reading all through the thread. Alternatively it's a thread I spend much time taking part in, only to have it locked because a mod's bored of it.
Sometimes it's worthwhile to lock up a thread - if it's a troll thread from the start. But it's annoying when a thread is locked whilst genuine discussion is going on, because of a few people flaming - why not ban those people? Or sometimes I see threads locked simply because the mod is bored of it, or thinks the discussion isn't going anywhere.
The ability to lock threads is the number 1 thing I hate about webboards; it's sad that people moved away from places like Usenet, where the control on what to read was in the hands of the user, not someone else.