nom wrote:Another thing to try (if you have the disk space): create a new partition for fresh install Yosemite and see if it runs OK. If it does, then it's unlikely to be hardware and more likely to be your current install - either something when wrong, or some cruft was carried over from a prior machine. On the other hand, if the secondary install suffers the same problems as your main one, then I'd take the whole thing back to Apple.
would not be very likely on a freshly PURCHASED unit (which I think is what we are talking about here).
Point blank, the "quality" of apple delivered product is declining from the prospective of defect count. Higher rates of bad HW, higher rates of bad initial images, etc. I wouldn't hesitate to request a replacement.