Feat prerequisites are gone. That also puts an end to feat chains. Racial and class exclusive feats are open to all as well. A few caveats:
No Epic feats.
Feats cannot give class features. You need to have access to a class feature for a feat to able to influence it. Example: Daring Outlaw does absolutely nothing without rogue. We can argue about the need for rogue. Any other class with Sneak Attack is fine as well. Bottom line: Daring Outlaw will nog give Sneak Attack.
Feats that improve on other feats need the original feat to work. Example: Great Cleave allows for multiple cleaves per round. But you nee Cleave to be able to cleave in the first place (Power Attack is not mandatory BTW). That doesn't mean that improved whatever feats are out. Example: Two-Weapon Fighting lower the penalties on two-weapon fighting. Improved Two-weapon Fighting gives an extra attack on the secondary weapon. This is not an improvement but an independent effect. Improved Two-Weapon Fighting can be taken independently from Two-weapn Fighting.