Great app, which will hopefully be perfect with an update. As far as I know, it calculates the Geohashing coordinates correctly (although I didn't check).
HOWEVER, it DOES NOT enter them into the map correctly! Sometimes, I end up getting the ocean near Africa for some reason, but other times, when it decides to give me a location that is actually within my Graticule, it is still considerably off.
I am not sure the reason for this, but the developer may need to look at the Map API more closely. It's not that the wrong coordinates are passed to the Map (AFAIK), but rather that either the Map doesn't like the format being used or the wrong method is being used, causing the Map to do further processing on the coordinates. For instance, the Map seems to want to put the pin on a known location, such as a road or building, rather than the exact coordinates. I was suspicious when the location was shown as being exactly along the middle of a trail, so I entered the coordinates myself, and it turns out that the true location is actually quite some distance from the trail.
We can also blame Apple a bit - COPY+PASTE, PLEASE!!!