I had an instructor go off on me for using VFR nav logs for planning an IFR cross country. This is the only time in my life that I've had an instructor yell at me.... and for no reason at all. For all practical purposes, using a VFR nav log for filing IFR is perfect! The only thing that doesn't work as well is fitting it nicely into your Jepp plate binder. As long as you don't mind having an extra piece of paper floating around, it's not an issue. Realisitically... beyond a checkride... all you really need is a plain ol' piece of paper to write your route down on, and you should be good.