[Herve5]

I downloaded the map tiles I need, and indeed they display without an active data connection. However, it seems that search for street names still require data, which makes the app pretty much unusable (unless you have all the destinations you want pre entered). Am I missing something or that's a limitation of the app?

I find like you and believe it is a limitation.
Even worse, when you prepare a trip by patiently downloading hundreds of Mbytes of tiles and then instead of following the preset trajectory you chose an alternative street anywhere, the guiding is more or less cancelled and the display shows you in the middle of nothingness. In my last trip (hundreds of Km) I stopped and patiently tried to relocate myself on an existing preloaded map, but the guiding never restarted and even worse, it seems attempting to launch it would bring me to a different mapscale that wasn't preloaded, so, indeed my dot was in the middle of nothing and with no guiding.
I bought this app on the idea it's the only serious, small-company-developped alternative to the current giants in the field (I definitely don't like monopolies). I would rebuy it today, on the same premises, but I definitely consider it unusable without a data connection --and I'm not sure indeed they'll ever succeed at it.