As a lefty who has shot IPSC matches with various 1911's formore than a decade, I canguarantee you that John Browning actually designed this pistolfor southpaws! Mag release and slide release are perfectly positioned for a left index finger. I would absolutely hate it if they were on the opposite side of this weapon. What else matters on this pistol except the ambi safety, which can easily be fitted for $30? Some might complain about direction of ejection, but after bazillions of rounds I've never cared.
Also own a HK USP with ambi controls, another good choice for a lefty.