Guidelines for using an unenclosed power supply?
You've got most of the right thoughts there in your lists. Open power supplies like that provide no prevention for water or dust intrusion. The big advantage they have however is far better air flow for superior cooling compared to the encapsulated brick type modules.

They're generally not used outside enclosures as stand alone units. They're generally integrated into products to save the manufacturer from having to design their own power supply.

They just need to be placed such that any unwanted contaminants won't get in. This includes random bits of wire or other loose material that could go around the shop. 

As an aside, for (what I assume is) LED lighting there are very efficient fully sealed AC to DC modules which wouldn't require direct air cooling, and could be sufficiently cooled by being secured to a heat sink. Some examples include these Buck Puck products from LuxDrive. I've used them, and they work pretty well.

Buck puck
BulletBuck

There's lots of other products on the market too.