Yeah, I tried to use it in rural ireland, and most houses do not have a number. However, even if a house had a number (and would show it on the map), searching it would still only ever give me the whole street as a result (Worse, often the first result was in a different village, hundreds of miles away...). Even in a well mapped major city area the search is very iffy about house numbers. As such I didn't even dare to do a more general search like "main train station".
Said that, it was usefull and other stuff worked great. Compared with the only other offline map I have used "here wego" (daimler, nokia, tizen) it does some things better, especially for foot / tourist type information, and you know, open source. But that search sure is an experience.
https://wiki.openstreetmap.org/wiki/Organic_Maps