You can assign VisualForcePage Tabs as custom tab pages.
I replace my SControl tab with VisualForcePage tab several week ago. It made my life whole lot easier. I don't have to deal with styling issue, and VisualForcePage allows me to focus on business logic.
Check out the new summer '08 feature for creating a default tab in an app which includes the customer portal. This allows you to direct the user straight to a Visualforce page (tab) upon login if, for example, you are looking to bypass the home tab for whatever reason :smileywink:
I replace my SControl tab with VisualForcePage tab several week ago. It made my life whole lot easier. I don't have to deal with styling issue, and VisualForcePage allows me to focus on business logic.