well finally pulled the trigger and upgraded my fishefinder. opted for the humminbird 598 with side and down imaging. had it out in the freashwater last sunday up at furnace lake.
initial impressions are I lvoe it. obviously the screen needs to be slighly biggers, especially for trying to place multiple sonar images on one screen, but given the size of my boat it is perfect (14' alum v-hull). Really, really easy to set up and actually get working immediately. the down imaging and side imaging are unreal with the detail they can show. have not had the opportunity to work the gps by marking points found on side imaging and getting on top of it with the down imaging and built in map. trying to get out there tomorrow and play around with it tomorrow and look closer into the controls and how to find fish better with it.
wound up getting the unit for just under 700 from an online source.