I think the edge is way too small to be usable. I have the GPSMap 76 but I don't think it is available anymore. It is barely big enough to be usable. What I like is its changeable batteries. But I don't think it is available ant more.
Have you considered a tablet PC? I have been using that lately to augment my GPS. The only thing I wish is that someone would add bike paths to the map. Google has it but you need to be connected online.