Garmin hasn't updated Mapconverter for a long time. It doesn't make .tgz files anymore, but it works fine on the Mac. The only issue that I recall is that the GPSFileDepot uploader won't accept .gmapi files, only .tgz and .dmg files.
I just did some Googling, and it turns out that making a .tgz file on Windows with 7-zip is trivially simple - who knew?

Assuming you have a folder named MyMap.gmapi that was created by Mapconverter, right-click, choose 7-zip > add to archive. In 7-zip, choose Tar in the Archive Format dropdown and hit OK. This creates a file named MyMap.gmapi.tar.
Now right-click the MyMap.gmapi.tar file and choose 7-zip > add to archive again. Choose GZip from the Archive Format dropdown this time. The default filename will be MyMap.gmapi.tar.zip, so just change this to MyMap.tgz and hit OK. This creates a .tgz file that works as expected on the Mac (I just tried it). I assume that you already have 7-zip? If not:
http://www.7-zip.org/I think the new .gmap format addresses a couple issues that we see in the forums all the time. It may be true that a small number of people want to store their maps in a special place, but it seems to just confuse most people. Since they choose a location for the map, they assume that they need to "open" the .img files in that folder. When that doesn't work, their next stop is usually the tutorial for adding .img files to MapsetToolkit and now they're
really lost. We see posts about this every couple days. For most users, I think it would be better not to give them a choice of where to store the maps and just use Garmin's default location. If they want the maps somewhere else, let them ask that question in the forums.
Another issue that I have seen (less frequently though) is that people sometimes just delete the .img files if they want to remove the maps. With the registry based maps, this confuses mapsource and it gives you a message about improperly installed maps and then quits. With the .gmap format, the user can just delete the folder and the maps will be gone.
I think trouble-shooting would also be easier with .gmap. If a user doesn't see the map in Mapsource, the first question would be to ask him to look in the Maps folder to see if it was properly installed.
But regardless, I can see the value to both types of maps. I am going to publish my next map in this .gmap format myself and see how it goes. I really appreciate the work Oz has done here in creating the installer, since that would have taken a LOT of trial and error for me.
