I've got about 2000hrs in C310s', and from what I'm gathering they fly just about like the 402s'(flown 421's also, not bad planes, but the flying characteristics are mainly weight driven I think). In the autopilots, there's supposed to be a flap compensator to add forward trim as you add flaps. It's pretty easy to hand-fly and do it also, just hit the electric trim about 1/2 second before you start adding flaps, and hold it down until the flaps stop moving. Other than that, great flying birds, love the airplane and would jump at the opportunity to fly in one again.
I've also been one to experience the one flap snapping up, the flaps are driven by a single electric motor, that has a chain/cable going off individual sprockets off the motor to their respective sides. Well one of those cables broke as i was going from app to full flaps. It initially made me think engine failure due to how the plane started rolling, but then I was all cross-controlled and engine instrumentation was fine. Took a few seconds to weed things out and clean it up for the landing, and all was well!