The Reasoning

Once you pass level 6, the full-attack is king. Virtually all of combat revolves around either gaining a full-attack or denying one to your enemy, forcing people to avoid other interesting combat maneuvers. This tendency only gets worse at higher levels, as the full-attack becomes a more and more powerful 'damage multiplier'. Saga fixes this quite simply, by eliminating the full-attack and changing several mechanics that revolve around the full-attack action.

The Rules

You no longer gain additional attacks from attacking as a full-attack action. Instead, you gain a damage bonus equal to half your level on all attacks. This does not eliminate the full-attack action, just the multiple attacks normally gained by it; you may still use a full-attack action for other purposes, such as stunting.

When using Two-Weapon Fighting, you may spend a swift action in addition to your attack action to gain your offhand attack at the normal penalty. Note that the changes to the Two-Weapon Fighting feat mean that you only gain a single additional attack.

The Commentary

Things which key off of attack rolls (especially Power Attack) should still work just fine. A mathematical analysis reveals that Saga-style attacks respond in almost the same way as Core-style attacks do to Power Attack; the differences are completely insignificant in practice and go both ways in relative power.