The stuttering that you describe when scrolling sounds very similar to an issue I discovered recently where the automatic brightness adjustment feature occasion

The stuttering that you describe when scrolling sounds very similar to an issue I discovered recently where the automatic brightness adjustment feature occasionally causes all multitouch gestures to be very choppy (including scrolling, but also swiping between desktops, activating mission control, etc. -- all of it). I understand you returned it so you can't exactly test this, but it would've been interesting to see if that particular issue was fixed by just disabling automatic brightness adjustment.