I just remember switching over at some point and not really noticing. Messages still made a small noise and slid in from the top right; some would disappear, some wanted me to click on them.
Like I said, I barely use the panel, and thought (thank you for the correction) that it was a later addition.
Ah, you may be thinking of Lion, which had notifications but not Notification Center. Notification Center is the name of the panel specifically, and that came one version later in Mountain Lion.
I just remember switching over at some point and not really noticing. Messages still made a small noise and slid in from the top right; some would disappear, some wanted me to click on them.
Like I said, I barely use the panel, and thought (thank you for the correction) that it was a later addition.