I was heavily involved in the Dreamscarred Press psionics work for Pathfinder, so I was interested to see what Paizo had made of their own take on psionics (which is, effectively, what this is), but haven't had the chance to until now. Given how let down I felt with the Advanced Class Guide, with a selection of largely mediocre or unnecessary classes, I wasn't too optimistic.
I was very pleasantly surprised.
The classes are much more original than those in the ACG, and in many ways while they have captured the flavour of psychic powers, they have avoided in many cases even coming close to the mechanics or style of the 3.5 psionics system. Some will count this as a plus, some as a failing - of the former, that's great, of the latter it is really clear that you can run the classes of the Occult Adventures right alongside those from DSP's Ultimate Psionics without any problems: the classes are different not just in name but in nature, as are their abilities for the large part.
The Kineticist - this class works a lot more like the 3.5 warlock than like any of the psionic classes, so much so that I couldn;t tell for sure if it was intended to be a replacement for a psionic class at all! It's much more interesting than the old warlock class, though, and more flexible. 9/10
The Medium - now this class is what the shaman from the ACG should have been, rather than the "meh" version of the witch casting divine spells it turned out to be. It's different, and I LOVE the crossover with the Harrow that has been thrown in with the spirit names. I haven't had a chance to play-test this properly, but I look forward to the chance. Again, there is no real psionic equivalent to this class, so it should run alongside psionic classes just fine. 9/10
The Mesmerist - holy cr*p they made Darren Brown a PC class! I like the mechanics of this, the mesmarist's tricks are fun and interesting, and the spells give them some utility outside of just staring into the enemy's eyes. My only concern is that this class may be too highly-focussed to work well in all kinds of campaigns. Again, in terms of psionics there's no clash with this class's features. 7/10
The Occultist - I think the use of implements shows that the designers really did their homework with this class. I like the way the class spells are limited by their implements, giving this class a great deal of focus and theme without mucking about with archetypes. Once again, the old psionics system has no clash with this class, it's a straight stand-alone that looks like it will work very well. 8/10
The Psychic - OK, this one is a take on the psion, that much is clear. But is it sufficiently different that you could stand the two next to one another in a party that they would compliment rather then clash with one another? Yes, I think so. The psychic has only four disciplines, and they are thematically very different to the psion's. They also play on different attributes, that make them different in flavour as well as in mechanics to the psion. I would play this class, not instead of playing a psion, but simply for it's own sakes. 9/10.
The Spells - some of these are directly lifted from the psionic powers, but you know what? That's OK. Powers and Spells have ALWAYS had a huge overlap, and that's never mattered before and doesn't now.
Overall I was very pleased with this offering, excellent work with a lot of thought gone into it, and a far cry from the ACG. Now if Paizo could put the same level of thought into fixing the monk... :p