I've searched, but not found anything quite about this subject. I have often had problems shifting smoothly in my HHR. When it's stone cold it's fine, probably because the shift is fairly slow, and when it's really hot outside (85F+) it shifts quickly, and the engine speed matches well for a smooth takeup in the next gear, but in between it's difficult to achieve this. The throttle seems to stay open for a while, probably for emissions minimization, and then it becomes unresponsive for a moment on pressing it again to get the speed back up to the matching point. I'm guessing this is maybe an intentional ignoring of a light pedal pressure lifting it out of idle mode.
I've tried every way I can think of to avoid this, but both holding the pedal down to allow it the speed to drop as the shift completes, and backing off completely and letting the revs fall then recover, but it just doesn't seem to ever work well, unless I shift really slowly. Any knowledge of a TSB for 'driveability' or similar?