I am currently running one, so far I have used it as a source of electricity damage to use against iron golems to slow them, a resilient sphere to protect a downed party member, cloudkill when confronted with winter wolves and also mass flame shield against same. Generally any good if situational spell is a good thing to keep in mind when using your shadow illusions. Also a good thing to try is to use it to imitate things with costly material components, like that magic tattoo spell or force cage.