I quite understand the doubts, but almost all feedback seems positive and a lot of folk think they are better than the Garmin ones.Thanks Monty,
I did actually download the OSM France mapping and installed it into basecamp to have a play with (not actually installed it onto my Zumo yet).
I'm just a bit nervous about depending on it 'untried' for foreign travel - wouldn't want to find out there are problems while away from home and computers / internet etc. These might be unfounded fears and It wouldn't be the end of the world - I've got maps and can read signs but I have got used to the (mostly) stress free experience that is satnav guided travel, especially in areas I've never visited.
Have a great trip, whichever way you go.
Matt