No it isn't. It is a standard game action. 4e codified such actions into at wills.prior to 4e people were not really walking around with this at will power concept.
An at-will power is anything that you can do at-will. These have existed in every edition. Same with daily powers. Encounter powers are the only novelty of 4E, and I believe they were introduced in 3E.
4E just gave those powers a name. Just like Napoleon Complexes existed before Napoleon.
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Warrior Melee Full Attack
You steady yourself, then lash out with a flurry of deadly blows.
At-Will * Weapon
Standard Action Melee weapon
Target: One creature
Attack: Strength vs. AC
Requirement: You must not have moved during this turn, except to shift up to one square.
Hit: 1[W]+Strength modifier damage
Level 6: Make a second attack against the same or a different target. This attack has a -5 penalty to hit.
Level 11: Make a third attack against the same or a different target. This attack has a -10 penalty to hit.
Level 16: Make a fourth attack against the same or a different target. This attack has a -15 penalty to hit.
Special: After using this power, you are unable to use actions to move, except to shift up to one square, until the end of your turn. If you have already shifted this turn, you cannot shift again until the end of your turn.