We ahve been going back and forth with naps for a good 5 months now or so. Sometimes she'll go a week without taking one despite having "quiet" time for a coule hours every afternoon in her room (she's so LOUD during that time, its hard to call it quiet). But then she'll nap every day for a couple weeks.
I think as they are trying to make the transition, the best thing you can do is still provide the time for them to nap each day since they still do need it a lot of the time. And then if they don't sleep, just move bedtime forward. We move it by about an hour, sometimes a little more if she's way too grouchy, so she's going to bed at 7 on no nap days, 8 on nap days. And she usually wakes between 7 and 8 either way.
~Kim