I'm very uncomfortable writing negative reviews - I know that a lot of work can go into getting something done, and it bothers me to write something bad about another person's hard work, but this seems to warrant it.
Eidolons Unbound is an interesting idea - there's a lot of work that's gone into this, and it provides some unique concepts for the summoner class. Unfortunately, it fails to mould these ideas to the Pathfinder ruleset very well. There are evolutions provided which the eidolon already has naturally, there are eidolon types which do not fit the established rules for eidolon creation, and there are feats which mimic summoner archetypes. There are some creative ideas in here, and with some rule-fixing (perhaps a version 2?), this would be a good, solid product.
If you don't mind sifting through the product and correcting it to fit with the Pathfinder rules, it is still worth the current price, but if it were to be fixed with an errata and re-released, it would be much better, and more than worth the price to get. As it is, I can't recommend this product in its current state.
[2 of 5 Stars!]