I have not update my MapSource since v6.13.7, for me, the main reason is that perspective is more important aesthetic. MapSource v6.15 and above, compresses the horizontal axis making the map and all objects in it look "stubby" and it is no longer WYSIWYG. (see the 2 screenshots at 5km scale). It gets more pronounce the more you zoom in. Furthermore, with v6.15.7 and above, Garmin has blocked unlock codes of third-party maps from working with it.
Here is the URL to get previous version of MapSource