I didn't like zombie sieges too much - most of the zombies are easily caught, but the remaining two or three can chase anything on the map for months, instead of going for traps, so military is needed to handle them.
Also the visitors are turning the DF into a reverse zombie shooter - they come in waves, and the couple of zombies have to dispatch them. Some visitors survive and enter the fort, most die horrifically. After one dies, another one instantly comes. Really, if someone needs an idea for the next zombie shooter, look no further. Dozens of visitors, seeking job, entertainment, scholarship or just sent on a spy mission have to enter enter the base, your team of hapless (but armed to teeth) zombies have to prevent this. Bonus points for style and evisceration. Even more for preventing resupply of the fort by caravan.
But later I noticed that many of the visitors leave good stuff behind them. And I'm not talking the crappy books detailing their pot-fuelled adventures. I'm talking about actual useful artefacts - including tables, doors, chests, warhammers, crossbows, shields and more. Since then, I actually like the sieges from time to time, because they are now like casino gambling (or fishing in computer games). What treasure will be next?
I usually have patience for only about 30-40 visitor kills before I sent my military to end the level, but it brings some joy to otherwise gloomy period. Anyone else values this... resource?