Apple is currently selling Xcode 4 for free, but when I try to buy it, it says I need to update to OS X 10.7 Lion. I am currently learning Objective C Programming, but the book I have is based on Xcode 4, not 3.2.6 (which I got from Apple dev website) Should I upgrade to Lion? I don't have that many apps that will be incompatible with Lion. I heard Lion has many bugs and Safari apparently hogs a lot of RAM? If I was to install Lion, should I do a clean install or just upgrade like Apple intend it to? Thanks very much. PS: Does Lion have support TRIM for 3rd party SSD yet? As I plan to get an SSD in the near future.