One simple measure of how much easier it is to perform common installation tasks with InstallAware, is to look at the steps required to read from a text file on a user's machine. InstallShield requires that you write a custom VBScript or DLL, which then must be integrated with the setup as an MSI custom action.
InstallAware's built in setup commands let you perform the task in five steps (which do not require programming skills) while completely avoiding the pitfalls of programming Windows Installer to perform a custom action.