If they adjusted it correctly, then it should shift at a higher rpm under part throttle where it should shift more smoothly. Didn't you say that it shifts more smoothly at higher rpm? I think at the lower rpm there may not be enough vacuum for the modulator to do its job - just a conjecture though.
1993 300e-2.8 - gone now <sigh>
"Do not adjust your mind, it's reality that's malfunctioning"