(imported comment written by BenKus)
After Microsoft releases the bulletins (usually around the afternoon Pacific Time), we work on the Fixlets in order of criticality on the most common operating systems.
Depending on how many bulletins are released, we almost always have the initial critical Fixlets released a few hours later and then we usually have all Fixlets released the same-day (Pacific Time). After we release the Fixlets, all BES Servers will gather within an hour.
For example, last two months:
September 2006 - 5 bulletins (including 2 re-release) - 6 hours
October 2006 - 10 bulletins - 11 hours
I believe the fastest we have ever released new Fixlets is something like 2 hours (there were 3 bulletins).
Many of our customers have very aggressive SLAs for patching and it is common for our users to have completely deployed the patches on the same day as Microsoft releases them.