Oh boy - I pop in here after forever and see that my fave tool is being discussed - yay!
I've been using Genome Mate for a month or so. Love it, love it, love it. I was so proud of my pretty, detailed spreadsheets, but I'd throw up a little and cry if I had to go back to them now.
I keep trying to promote Genome Mate in the Ancestry thread at 23andMe whenever people complain about trying to get a handle on managing their data or FTDNA's current bug with the match dates (which affects us a bit less, since we can see who is new when importing the CSV file into GM). Alas, I probably just come across as a spammer.
I hope the app eventually has a way to export the "Segments" list for a given test. (Or have I overlooked this feature?) Otherwise, it seems pretty perfect. The clean notes, the color-coded ancestors on the graph, the custom groupings, and the beautiful import capabilities... people who manage multiple tests and who are still using spreadsheets don't know what they're missing!