First up - this review was written before actually trying out the class in play, so may be updated at a later date.
It's rare to find a new class that actually adds something unique - but also desirable - to the game. The Reflectionist does, and pulls it off pretty well.
The core concept of the Reflectionist is really strong, and does a great job of differentiating it. In practice that means it has a new playstyle, and a nice range of abilities without treading on the toes of any other class. The subclasses flow logically from the main concept, and make sense. None are obviously better or worse than the other (though the last option will require some planning and a strong character concept to make best use of).
Between the core abilities and the expanded, optional ones, it's easy to draw comparisons with Warlocks, and it does look as though the Reflectionist would match them for versatility.
I'm highly excited to try out this class and see how it actually plays!
[5 of 5 Stars!]