Navicore on the 770 is not bad. But you shouldn't make the mistake and update the software. The new version (which looks identical to the N800 version) seems a bit unstable (crashed twice on me while driving when doing a re-routing). The previous version didn't have this problem. Also the new version seems to demand more RAM and sometimes I can only start the program after a complete reboot. Even with 64 MB of swap space enabled.