Fran wants to know if she should upgrade to OS X Mavericks if she buys a 21" iMac from Apple. Leo says it's odd that Apple is shipping their latest hardware without Mavericks. It should already be installed. If not, she can easily download and install it from Apple. It's a free upgrade. What about a fusion drive? Leo says it's not really worth the extra price. She should go with either a hard drive or, better yet, an SSD.