I used the heck out of it last night! I typically leave a LOT of stuff in the vault. Super-important items like exotic shards (don't want to accidentally delete them in the heat of battle) and mundane things like weapon parts (to make room for other things) In Crota - got upgrade for gauntlets. Dang, don't have enough sapphire wire! Open phone app, move item . . . poof! Able to upgrade gloves! Got upgrade for Alpha Lupi chest. Dang, don't have enough Spirit Bloom. Open phone app, move item . . . poof! Able to upgrade. It happens almost instantaneously. You can do it in the amount of time from when you activate the crystal to when the windows drop at the beginning of the Crota fight.