A new paper in Astrobiology makes claims for possible biogenic origins of structures seen in Martian meteorites. A not unreasonable response is: so what?
If the astrobiology fairy tomorrow gave us incontrovertible evidence of (at least) previous life on Mars, there would be massive public interest and a lot of opportunities for astronomy and basic science in general to get funding; and a whole new surge in interest among young people around the world. Consequently an unqualified "so what" might be the wrong question; "so what in terms of impact to scientific knowledge" is more appropriate. We expect to find life eventually, based on our understanding of the origins of life on Earth. Finding evidence of ancient Martian cells would add more support to our picture of an ancient wet Mars. We might, just might be able to infer something about the cells themselves, but this would be very limited. So life on ancient Mars wouldn't actually be that surprising!
Finding living cells on Mars would be huge. There's definitely a non-zero possibility that cells on Mars and Earth might have the same ancestors, which would actually be kind of boring, but would tell us something about the diffusion of life. But seeing such a novel biochemistry in action, even one that is ultimately related to our own, would give us a lot more information that we could use to understand evolution, biochemistry, and complex systems.