Peter Hines of Bethesda has stated that in Oblivion, SIXAXIS is not neccessary and personally he would've rather seen rumble implimented into the controller.
IGN: Did you ever think about including SIXAXIS motion support?
Pete Hines: We didn't think about doing anything with the SIXAXIS stuff. We just wanted to make sure it played well and doing something new with the SIXAXIS just wasn't even necessary. Obviously if we ever have a game that would work well with the SIXAXIS then we would consider using it… but that wasn't an option for Oblivion.
IGN: What do you think about SIXAXIS?
Pete Hines: I think that its value depends upon the game. It didn't make sense on Oblivion but I'm sure there are some games it does make sense on. To be honest I would rather have the rumble instead of the SIXAXIS motion stuff.