Have done it both ways and am much more comfortable just winging it! We are of the mind set that if it was meant for us to eat somewhere, we'll get in.....if not, we'll go somewhere else. I would make a PS for a special occasion or if there is a special restaurant that you just have to go to. Other than that, we just go with the flow as it just makes it easier not having to be on a schedule to eat while we are enjoying WDW.