PSU Bypass Caps

Well, I'm almost done my PSU, and my question is can I get by using some 100nf mylars I've got lying around as bypass caps? Or should I wait for an order of polypropelenes? Also, do values really matter, could I use say a 3.3uF poly cap (because I ordered some for an xover, but decided to get some extra in case)? I'd rather just use a couple mylars per rail, but if it really matters I guess I'll wait. I can understand in passive xovers going with polypropelene, but for bypassing a psu electrolytic, a polypropelene shouldn't be that much better then a polyester, should it?