Drdepth does a good job with data spikes, has comprehensive editing features and weeds can be dealt with. It is really an issue with your sonar and its abilities, give any contouring software a bunch of false depth points and you get false contours. I used humviewer with drdepth to correct a survey thru very thick weeds. Posted about the process on the yahoo drdepth site. Lots of work ,took sidescan data for a mosaic ,now have an accurate contour map and know the weed beds very well. So a two edged sword , lots of editing needed , but the editing and mosaic provide info on the thickest weed areas and holes .
If your sonar locks on to the other objects mentioned you have data spikes, depends on number of false points, easy to spot and fix in edit mode. All versions have waypoint capability with access to garmin ,hb and lowrance waypoints. Also custom waypoints can be created called user waypoints. No problem to export waypoints to different units.
Maps as .lcm are supported by lowrance units, easy works well. Hb units accept contours as tracks, very frustrating and limited .
If you have a sidescan sonar the ss version is great and keeps getting better. Download the demo version ,read the help files you won't be sorry.