As the quote goes, "You cannot NOT have a user experience". User experience is one of the most important things in product design. I personally feel that Siebel's User Interface could be a lot better than what it is (but thanks to the new Innovation pack for 2012, with the Open UI I think Siebel is getting there).
Most users do not like drilling down on a record which then takes them to the detail view of a record and then navigating back to the parent record. What they usually ask for is, if they could have the tabs right on the main view of the screen. Something like this -
Some thought this was not possible but actually it is and requires just a web template change for the Aggregate views.
Change the Web Template of the view to either one of the following -
1. View Parent Multi Child With Tabs
2. View Parent List With Tabs
Cheers!