Haven't had to deal with this myself, but DST must complicate fixed shifts as well ? (If you're on shift from midnight till 8am when the clocks go back, do you work 9 hours ? You wouldn't necessarily get the hour off again when they go forward, as it may be someone else's rota on nights.)

The really messy one I've come across is working across two offices in the northern and southern hemispheres; changing to DST on different dates and in different directions.