@rcjmaxx: You could use only one switch, but if using a UBEC, I too like to use a seperate switch for the receiver/servos, but only in between the UBEC and rx/servos. When you first plug in your batts, the UBEC output may need a second or two to "settle down" since it's a switching device. Then, I turn on that switch when the power is stable. Then, I turn on the ESC switch. No problems thus far.
If using the BEC built-in to the ESC, just the ESC switch is fine.
@gd: Yeah, I hate those cheapie open-frame switches. dust gets in there and the contacts get all yukky (that's a technical term :)). There are closed frame switches that you can solder on there and then plastidip to really seal it. I don't want to remove it because I still use the switch to calibrate the radio after software updates to the ESC. I am planning to pick up several of
these and swapping all the open-frame switches I have right now.