Re: longevity, ITP didn't find any significant impact from metformin. Afaik they're the most rigorous testers of this sort of thing, so that's pretty significant to me.
>Metformin (0.1%) combined with rapamycin (14 ppm) robustly extended lifespan, suggestive of an added benefit, based on historical comparison with earlier studies of rapamycin given alone.
Interventions Testing Program (by The National Institute on Aging) for the unfamiliar, like me.