Okay, we're staring winter in the face, holiday gifts are on deck (including gifts to oneself...), and it's easy to get bored. There are Nav IV's and Garmin Zumo 600s and 660s out there to be had at reasonable prices. My 2720 works fine. Boots up quicker than the 550, seems to freeze up less, and the various windows are more customizable. The Nav IV is thinner and lighter, can be used on battery, and is at least reportedly newer tech. Has anyone made the swap between these two who wants to opine here, to either help me spend or keep me from spending money?