I was part of the kickstarter that brought this product to fruition, and have been using this for a while. The classes inside are, for the most part, fun and interesting to play with. There are a couple balance issues. The carcaster's YuGiOh archetype is a bit of a mess and requires what feels like a fair amount of DM fiat to be playable in a long term scenario. The Moorph suffers a fair amont, as well. The saving throws disobey the 'strong and weak' rule that some homebrwers might be aware of. But aside from that, there aren't a lot of beasts to actually transform into, making it's greatest strength, the ability to turn into higher CR monsters than a druid, difficult to work with. I've allowed the use of monstrocities, which are basically beasts with elemental powers, and this has worked well, though may be too powerful like that without some serious planning on the DM's part.
I haven't playtested with every class, yet, but for the most part these are spectaular and I do not regret my purchase in the least.
[4 of 5 Stars!]