This add on works fine with addresses, even "unusual ones" like "N5 6-7, 68161 Mannheim" and GPS coordinates like "49.483572,8.476893". As nomade0 desired and I would have also desired, too, the context entry is already named "Search Google Maps for" instead of "Map with Google" - good.
Just one thing missing: Optional search in Open Street Maps as 1) it offers much more detailed maps and 2) has coverage in some areas that are mostly "white" on Google Maps, e.g. mountain parts of the Alps, Iceland, or Peru. I'd also be happy to be able to provide a context menu name and the search string URL myself, just like for usual Firefox keyword searches.