I have been less than impressed as well but I haven't spent that much time tinkering with it yet. Have been more focused on wetting the lines. One thing that I have noticed is that I need to be going slow (3 mph) for it to give me clearer images anything over 5 and it is messy. Think it has something to do with my hull design creating too much air being stirred up going any faster.
Did you update the firmware? I bet your problem with SI is that the transducer isn't level. It needs to be a close to level as it can be when the boat is moving. Reduce the coverage distance to < 75'. I have been running at 50' to see what things look like. I see a pile of rocks or a down log and then drive by it.
Also get a micro sd card and record a trip. When back home you can review and tinker with the display settings to make things pop out.
As far as settings and videos check out stuff from Doug Vahrenberg on you tube. Doug and some of the HBird gurus are all over the BBC board. Some good information.
http://www.bbcboards.net/forumdisplay.php?f=133
Here is his recommended settings.
