If you install Solaris on servers using jumpstart then you never actually see Solaris interactive installer. But more and more people are using Solaris on their desktops and laptops and often installer is their first contact with Solaris. And I must admit it's not a good one. Fortunately Sun realizes that and some time ago project Caiman was started to address this problem. See Caiman Architecture document and Install Strategy document. Also see early propositions of gui Caiman installer.