I have been using a fl20 for 4seasons now, great flasher, just got a LX3tc as a second unit after (some bad luck with my showdown), I will be using it over the next several days and will post a review it will be side by side with the fl20, it looks like a great flasher, and marcum is probably the best company I have ever delt with, when my showdown was acting up they took care of me in an instant.
Tried may new marum LX3 yesterday, only 3feet from the fl20, very compatable, little interference in both units but cleared up no problem, the LX3 is a very nice unit easy to use, not crazy about a hooded screen you have to sit right in front of it to see it, I don't know how someone can come on here saying that the marcum is better than the vex, its just not true, vex is has a better display, nicer colors and is larger, in what way is the marcum better? Its not, but still a good unit, the very small screen is marcums week point.
My other two buddies I fished with were using the HB 35 this unit is hands down the best unit for the money, just don't buy 2, the interference is aweful even from 20meters way in different shelters, although the HB 35 has no problems with the marcum or the vex.