Being a GSM yes it's a very handy skill to use. However Manipulation competes for a cross-class slot on other classes - but this depends highly on your rotation and your stats, so my point could be moot if you don't use Inno/Inge2/RS/Reclaim (any 1 or 2 of these), and the amount of CP you need (referring to the minimum # of ToT procs) to actually finish the craft.