Personally, saving older devices and having them available is a PITA for most esp. if you are mobile, so...
tl;dr - download older versions of Xcode, grab the iOS Simulator packages and install in your existing Xcode http://blog.chpwn.com/post/19662817128 Once we nix the 3.x requirement, we can just do this through Xcode -> Preferences -> Downloads where we can still download iOS 4.3 Sim
