Yesterday I put a npc kineticist into my campaign for my party to take on.
He was a 4th level Aether kineticist
Initial observations:
Aether Kineticists have a distinct lack of options if you dont want to go the route of light touch at low levels. And as an npc that sort of thing isn't generally valuable.
How the encounter went. He attacked in darkness, at the edge of the party's light, hurling rocks and debrie at them with telekinetic blast. He tried placing kinetic cover, but it was more or less useless particularly given it was a standard action. His force ward was basically meaningless even against lower level opponents, 4temporary hit points that wont regenerate within the encounter is basically nothing. It was gone in one shot and he took a fair bit of damage on top of it.
He did do a lot of damage, at low levels at least, the kinetic blast did plenty of damage, and his to hit was fine even against normal AC. Again this was 2nd level characters, but still, at low levels at least I think the attack bonus is sufficient. The damage of the telekinetic blast definately put some fear into the players.
Kinetic cover being a standard action, was basically a waste of a turn, since its static, people just moved around it once they realized it granted cover. It might be more useful in a larger scale combat with more combatants, but by himself, it was a certain waste.
Overall, I think the kineticist makes a good npc enemy, good damage, simple to run, and something different. But as a party member its sorely lacking in terms of filling one of the traditional four roles, I think some added utility, and either the ability to effectively deal with negative conditions (expanding kinetic healing), or the ability to be the magic knowledge guy (spellcraft, identifying magic itesm etc), or significant skill points and more class skills to be the skill full character, as it stands its a pure 5th wheel class, without a place in a 4 person party unless the other 3 are like a druid, a summoner and a bard, and are already a functional party without the kineticist.