So I have an external back up drive which has a CCC backup of my internal drive. The backup drive was last updated prior to updating to Mavericks on my internal drive. Therefore my backup drive is bootable into ML 10.8.5. I've been running Mavericks since 10.9.3 was released and haven't experienced any issues with it. For me it has been running quite smoothly. Would it make any sense to keep my ML backup and simply update the contents (can I even do that?) or just write over it with Mavericks. I can't see a reason to go back to ML at this point. My backup drive which is 1TB is partitioned in to two equal spaces. My entire contents fits on either half.