You can only take apart 3 spells per day with Arcane Manipulation.
That's probably plenty for me... well, 4 would be nice but I can live with three. I'm now being tempted by Versatile Spellcaster though. The more I think about it, the more I see that it gives me flexibility I simply do not have, while Arcane Manipulation is just improving an ability that Rary's Mnemonic Enhancer already gives me. It's hella expensive, but when you simply HAVE to have that Transmute Rock to Sand spell that you have only actually memorized twice in your career... The cost beats the time and expense of crafting scrolls, too.