I recently came across the depression awareness campaign that Samaritans of Singapore ran a few years back featuring ambigrams in their ads. The artwork was done by the Publicis Agency.
All in all I think the first design is lovely and the backgrounds are striking. The other two designs have a few troublesome spots & I could sit down and analyze what spots I would change, but I'm fighting the urge. Either way, it's always exciting to see ambigrams used in ads!