I have memory map and it is truly awesome softwear expecially the 3d facility. I've recently been given a Garmin Oregon 300 GPS and it has a facility to upload maps and I got the whole UK topography map with it-which is great but not as detailed as memory map as MM is OS maps. Garmin have released the national parks at that scale on a card that slips into the gps and I'm waiting for them to release the whole of the uk, these will cost around £30 (so the guy said when I went in to buy one last week and he told me they are not released yet.) in Tisos which is excellent value for money.
I don;t think memopry map is compatable with Garmin? I certainly cannot get it to work on my GPS, so i'll need to go with whatever Garmin produce, but Memory Map is exactly a reproduction of OS maps and they are awesome to use.