I think ian c hit it. you want to avoid driving around at the variocam roll-over points to keep from having the flappers and cam knocking back and forth. cams actuate at 1500 and 5500 rpm, and resonance flappers at (I think) 4000 rpm.
regarding resonance, I don't think there is anything definitive on that which I have seen. pedro is a nice guy but not a mechanic so i'd take that with a grain of salt. I think the 3000 rpm thing most likely comes from the vibration that some folks experience at that rpm range. I get it in my car and, depending on what you read, have heard that it is due to exhaust resonance, failing dual-mass flywheel or failing motor mount. ie, some sort of overall vehicle vibration and not a driveline/bottom end issue that will result in the engine rattling itself to death. the dmf is there to address any potential engine harmonics and it's a whole other argument as to whether cars with lw flywheels have any excessive vibration/harmonic resonance issues (that result in broken cranks, etc.).
to southernstar, I would suggest that gentle braking is harder on your brakes than hard braking - more heat gets introduced into the system if you brake for a long time vs a short time.
personally, I do everything to keep the tach right of vertical at all times. mechanic tells me its the strongest 3.2 he's ever seen and oil filter consistently returns a clean bill of health.