I agree. I'll use manual 6 until I start climbing a grade. I set the cruise control after in manual mode because it will kick up the rpms momentarily having it in Drive then going manual and vise-versa.Not mine either. I notice that if I switch from D to M then it shifts down a gear while cruising. I do notice that the cruise isn't as smooth when switched on. It won't "activate" until my foot is clearly off the pedal and then re-engage the acceleration. My 2004 TL smoothly engages the gas pedal as I let go if that makes sense.
I usually drive in the normal auto mode, the RPMs jump no matter what speed I put the cruise on at! I will test and see if it happens in eco and sport mode too!That doesn't sound right. I just used mine yesterday and the rpm never changed. Were you in manual shift mode and what was your speed?