Upgrades
Upgrades can be applied to feats and powers as noted in their description. You must apply all downgrades first before you can apply any upgrades.
You cannot apply downgrades to an effect if it would reduce its tier below 0. For example, you could apply up to three -1 downgrades to a tier 3 effect (reducing it to 0) then apply a +3 upgrade to it to increase it back to tier 3. You could not apply a -3 downgrade to a tier 1 power and try to offset it with upgrades because you have to apply all downgrades first.
Mundane upgrades can be applied to basic actions, increasing them from having no tier actions to having a tier equal to the total of the upgrades applied and causing them to cost MP like a power. For example, Defensive Gambit can be applied to any action that grants you the benefits of the Defend action (including the Defend action itself) allowing you to take attacks of opportunity while benefiting from the Defend action.
In addition to the effects below, metamagic feats are now called augments. Augments function like upgrades but instead of being applied to one power, they can be applied to any of your powers assuming they meet the prerequisites. However, augments consume double the normal amount of tiers. For example, the Quickened upgrade reduces the time needed to activate a power by one step per 2 tiers. However, learning it as an Augment would change this to one step per 4 tiers as it would be flexible and able to be applied to any of your powers, not just the one you upgraded.