I just bought the HDS-7 yesterday and used in on Eufaula today. I bought the one with the preloaded maps. I have this one mounted on my dash and a different Lowrance on my bow. The one on my bow has the Navionics 2008 in it. I can tell you this, the Navionics chip has better detail on contour lines but the preinstalled HD maps shows the river channels better. Supposedly you can't use the Navionics with the preloaded maps right now. There's supposed to be a software update in the next week or so to correct this problem. Personally I think the preloaded maps are good enough to not worry with the Navionics chip. Just My Opinion. BTW I love the new HDS-7 and can't wait for the side imaging transducer.
To heck with work, lets go fishing.