My auto does not at all feel like I'm getting rear ended but it will do a "clunk" into 1st very rarely.
What is more common is I will feel it "kick" into 2nd when my foot doesn't have enough pressure on the gas. Like I can "feel" the shift when my foot is very light on the throttle. Nothing like your describing though.
It's weird, but I stopped caring about it.
Any performance tuned transmission will exhibit characteristics like this in regular driving. I have driven the Porsche pdk 7 speed, BMW dct 7 speed and the Mercedes Benz 7 speed and they all have this "clunky" sensation when not being ran hard. The Porsche being pretty bad. It will jerk your head back and forth and actually bang into gear at low rpms when it's being run at part throttle and you don't use the tiptronic to control the gears.
When my foot is meeting the floor is when the tranny is at its best. Most "performance tuned" autos are like this. Sent from AutoGuide.com Free App