I use 'em and they're fine

With regulator you'll get a constant voltage straight off the charger. Without regulator you may get a bit of servo 'jitter' whilst the pack voltage is still very high straight off the charger - a bit of stick waggling to take the sting off the pack and all is well.

You'll also get the benefit of maximum torque and speed over 4.8v

Very few servos nowadays won't run off 6v.

Rgds,
Mark