What is so great about Anyspell?


I have seen it rated gold in many guides, but no reasoning was provided.

Sure, you can cast Invisibility or Glitterdust now, but it is once per day, using a 3rd level slot, and you need to have access to the spell in written form.
This does seem nice, but too little to matter.

Is there something I am missing? Can a Cleric activate a wand if the spell is in his head with Anyspell for example?