While I don't have any plans to add an ambi safety to my Sig C3, I can say it takes some getting used to taking the thumb from a grip position over to the fingers side of the grip to flick off the safety. One handed reloading practice has been using the shelf at the range, since I don't think the rangemaster would smile on me working the pistol with my knees...
That said, at ranges from 10 yards in, I am confident I can hit a stationary paper target within the kill zone of the reduced silhouette. On a moving or returning fire target? Hope not to find out.
I do practice at least 25 rounds of weakhand per session, though. Some days, I will do over half my shooting weakhand.
I have noticed a tendency to hit slightly high and right when shooting lefthanded. Working on that one.