I'm not going to talk about the psychic or mesmerist much here. The psychic gets to be the magic and magic item section, and it's a mixed bag. Mesmerist just isn't a class I much care to play (outside of one archetype), so I haven't spent much time looking at it.
Spiritualists get a nice chunk of stuff, a fun new emotional focus (and rules for using it with older archetypes). Two new archetypes, one bringing in some black blade magus fun, and a phantom animal one. I have intentions of using the phantom blade, the totemist I might if an appropriate campaign comes up. My only real problem with either is they lose emotional focus (something I enjoy about the flavor of the class).
Medium gets a fun new archetype. It doesn't really address any issues with the class, might even make some of them worse (forcing taboo). It get's fun abilities and has cool flavor though. Look for a thematic campaign to use it in.
Kineticist gets a lot of expanded selections. The invocations are a cool idea, and possibly a good tool for the future, but the feat look for most characters is disappointing. More talents, especially for wood and void is nice. Wood's new simple blast is disappointing, and makes for a (mostly) true pacifist if taken as your first. Not practical but interesting choice. More blade abilities make the melee fan happy. Speaking of which the Kinetic Knight is everything I ever wanted for the Kineticist, not just supporting but encouraging a strength based build, nice defensive features. I've already started playing one and it's one of m favorite builds. The lack of form infusions can be limiting somewhat though.
Occultist is another nice package here. The panopolies are great. Between giving you a way to go deeper into your spell list with out giving up too much versatility and some nice new focus powers. the archetype to support them is a nice addition too.
Overall a great book that supported the four psychic classes I care about in fun ways, and inspiring at least 4 new characters I want to play.