The Lowrance HDS-7 comes with Insight USA Maps pre-loaded and has options for no transducer(if you have your own), a 50/200 transducer for saltwater fishing, or a 83/200 transducer for freshwater fishing. You can also choose to get the additional LSS-2 StructureScan HD module to see Down Imaging and Side Imaging on your Lowrance HDS-7 screen.
This fish finder is an amazing device that blows all other units out of the water. It is meant for fishermen who are competitive and want to up their game to a level where no one else can match them. You can integrate your entire boat to be controlled with this one Lowrance HDS-7 unit.
This fish finder falls under the "multi-function display" category. Multi-function displays do much more than just fish finding -- they have GPS, radar functionality, advanced radio options for satellite and VHF, and integrate much more deeply into your boat. You can also hook up your engine to monitor fuel, and you can also get your boat's audio system synced in, too.
While the HDS-7 is a little more expensive than other fish finders, it's well worth the investment if you get your full potential out of it. If you are just buying it as a showpiece on your boat, it's good, because it has a nice big screen, but there are other options for that, too.
Tournament anglers prefer the Lowrance HDS series units because of the StructureMap function that lets you overlay side imaging data on the map, so you can see both SONAR and your GPS position in one screen. A few days before a tourney, you can go out and map the entire lake's structure so you know exactly which spots are the most promising.