What’s so great about Shalantha’s Delicate Disk?

In a recent comment, Hey I Can Chan mentions that he has found the spell Shalantha’s Delicate Disk (Lost Empires of Faerun, p. 33) to be sufficiently powerful that he avoids using it when DMing due to balance concerns.

What’s so impressive about this spell? Is it:

  • The ability to pre-cast spells with long casting times, then trigger them with a standard action in combat?
  • The ability to load up on Disks during downtime to give yourself extra spell slots down the road?
  • Some other trick I haven’t thought of?