I just recently got the Navionics East map chip and I think it's definitely worth it. I also had the iPhone app before getting a plotter with gps and while it was ok, it's nothing compared to the actual chip.

The actual chip gives much more detail with more contour lines. Also, it comes with a reader where you can view the map on your PC and plan out everything at home before you go. You can even set waypoints from your PC I believe, although I haven't done that yet.

The problem I had when using the smartphone app, was that the gps didn't update very often since it used cell towers to triangulate your position instead of actual satellite signals. Since it seems that I don't get very good cell service on some of the lakes I fish, that really hurt the effectiveness of the app for me.

I'm not sure if it's worth the extra $50 for the platinum maps or not, as I don't think the HD bottom scans are of any of the lakes in our area.