It's a free action to store as well as retrieve.
I find that it's most useful for Clerics or Fighter/Wizards. It allows them to always have a hand free for casting spells with somatic components, while also being able to fight with a weapon and shield. You just store your weapon (as a free action) when you need a free hand, and then retrieve the weapon (again, as a free action) afterwards.
No more dropping and then retrieving weapons or shields ever again! Plus, they are only 2,200 gp each, so you can get one at a fairly low level. In some cases, it even removes the need for Quick Draw.