Witch has made a great survey of Downtime among various hacks, and considerations when changing it.
The bit about the push & pull between the fiction and mechanics for entanglements was my favorite part. I hadn’t thought about the usefulness of defined approaches to addressing entanglements before, though I still prefer open-ended ways to do so.
If you’re designed a game with downtime, or just want to improve your sessions this is well worth reading.