The Mystic class is similar enough to other spellcasters to feel familiar, but different enough to be interesting. The fundamentals of psi points and psi limits are well balanced compared to other classes.
Once or twice you might notice something like, "they forgot to put a duration on Darkness, hahaHAHAHA" and then your group brainstorms for a while and comes up with something. These should be interpreted as a heartwarming opportunity to bring your group closer together. Same with errata in other products like the Player's Handbook or whatever, so it's cool. :)
Free to download, so give it a look, maybe one of your group will feel drawn to try something new.