In my experience, a TVSS at the outlet is not very useful, as the long path (romex ground or BX armor) back to earth ground has relatively high inductance. A combination of lightning arrester at the meter and TVSS at the panel (both with a heavy, low reactance path to earth ground) would be the way to go.
At individual outlets, RFI/EMI suppression is a good idea, both at sensitive electronic equipment, and devices likely to "dirty up" the powerline.
