Since this is a blog for folks new to OSX, here's a bit of sage wisdom: never install an update from Software Update for the first five days it has been available. Over on Macintouch, some people are saying that 10.1.3 has crippled their previously-fine systems. There is nothing urgent in 10.1.3, and I would say wait until next Monday, and then only do so after reading some of the other Mac forums.