With any kind of group deployment it's always best to take the time to test SP1 on a guinea-pig machine, whenever possible, to see if SP1 causes any changes in behavior for a typical system's application set or hardware. Also see if there's a difference in behavior between patching an existing system (i.e., #1, #2, #4, and #7 above) vs. recreating the system from the ground up (#3, #5, or #6), depending on what'll be most efficient for your organization. For instance, if you're planning on updating a great many applications along with the system itself, a full system re-image might be the best choice, depending on how much is being installed and in what form.

If necessary, SP1 can be uninstalled just like any other Windows update.
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Individual users may want to take advantage of SP1 as an opportunity to install Windows entirely from the ground up -- a way to do a clean sweep of the accumulation of a year or more's worth of clutter. This isn't a bad idea -- in fact, it's something I've done myself with XP SP1 and SP2 -- but it has to be approached correctly, and it does take a fair amount of work.

For one, you'll need to make a quick inventory of all the third-party applications and crucial system drivers that you need to reinstall after swabbing the deck. If you have system drivers that were not installed by Vista proper -- mass-storage drivers, for instance -- make sure you have those in hand before you start setting things up.

(Tip: Place any drivers needed for setup, such as mass storage controller drivers, on a removable USB drive if you have one. Vista can read from such devices to obtain drivers during the setup process, and you can cram a lot more onto one such drive than you can into any number of floppies or even a CD.)

Note that unlike other Windows service packs, it's not possible to apply Vista SP1 to an offline Windows Vista image, due to changes in the way the service pack is packaged. The Winbeta.org site has outlined an undocumented method to do this (not attempted by me), but it's rather complicated and requires a fair amount of legwork, and of course there's no guarantee it'll succeed.

Finally, Microsoft's Deployment Guide for Vista SP1 (currently updated for the release candidate of SP1) goes into detail about all the above methods, and provides links to additional tools and guides that ought to come in handy during a rollout.