For many situations, yes. Taking a pay advance when you PCS is a great way to help yourself out get ahead financially and stay out of debt while you PCS. There are many costs associated with a PCS, not all of which are reimbursed.
A pay advance is a 0% loan to your present self from your future self. You can usually get a month's pay (BAH + Basic Pay, no BAS or incentive pays usually) advanced to you (with the taxes taken out) and then pay it back over the next 12 months. It's a fairly painless process that can usually be accomplished through your online finance office or in the finance customer service area on one form. If you only take a month's pay out and repay it over 12 months, you don't even need a commander's signature: it's automatically approved.