This map editor is amazing. As others have said its strength lies in its simplicity. Even in its alpha form (presently v0.10) this mapper is a very useful DM tool. I'm using the DirectX version on Windows and it works flawlessly. I look forward to whatever improvements come out next, but even if this were the final version I'd still be happy with my purchase.
I'm currently running a dungeon crawl campaign and I draw my maps on a Mondomat in real time as the party explores. This works well during the sessions, but since we only play a couple times a month the party has trouble remembering where they've been and where they wanted to go next.
This tool has allowed me to draw high-quality digital versions of all the maps in my campaign, which can be shared with the players as they progress. It is now trivial for me to maintain DM and player versions of every map. After each session, I update the player maps based on the party's progress and share the PNG and JSON files via Google Drive.
The free online version is also very nice to have because it enables my players to add their own notes to the shared maps.
Well done, and please keep up the good work.