I always pigtail the neutral when installing a receptacle. It has nothing to do with series or parallel. (whether or not you pigtail it, it's still wired in parallel) I do it so that the next electrician to come down the pike won't have to deal with breaking the neutral to the rest of the circuit if he has to replace the recept.
If the recepts are part of a multi-wire branch circuit, 300.13 prohibits using the device as a splice anyway.
