Kizza, my install has not affected the performance of 2012. Because they run as separate programs, I do not think you need worry about 2013 infecting 2012 with its glitches.
I would like to say that I am unlucky or that it is a local problem, but it is happening to other members of my office. It could be we are sharing a configuration that is causing the problem. We are all running 10.6.8 - we have not updated to Mountain Lion.
I have found that even simply in 2D I get crashes for "no reason" - to say that they do not follow any action, but simply occur while navigating around a document or clicking back to a document. I have moved rendering back to 2012 for the time being.