RCGUY:

These guys are correct. Especially with the HiTec servos which are supposed to be capable of taking up to 10 volts (I don't believe it as a constant 10v, although I maybe wrong). The only servos on the market that don't tolerate 6v too much is Futaba. They are marked as such although their digitals are more tolerant of 6v when it is regulated. As these guys pointed out with a regulator you get a more consistent voltage through out your flights. The regulators used today are better suited to battery packs of Li-Ion & Li-Po technology where the voltage out is any where from 7.2 to 8.4 volts and needs to be regulated. As pointed out a 5-cell 6 volt NiCad or NiMi doesn't need regulation with todays' servos.