I used the Humminbird 997SI for a couple years and it was very cool but I was never really able to apply it to more fish caught. Probably because of the topography and water clarity of the lake I mainly fish.
As far as electronics go, I've been alot more successful with the use of very detailed, accurate chart maps such as the Lake Insight on Lowrance's newer HDS stuff. They also now have the ability to shoot sidescan (StructureScan) which is something I plan to add on soon.