Welcome to the site and congratulations on becoming an S5 owner!
Have you been driving in mostly 'S' (Sport) mode or in 'D' (Drive) mode? I have found that when driving in Sport mode, I can feel some of the shifts taking place. This is particularly noticeable when I'm slowing down to come to a complete stop and the transmission is downshifting. However, when I have the car in Drive mode, the shifts seem much more smooth and I don't really feel it shifting gears unless I'm driving the car aggressively. Since I've never experienced a Multitronic, I can't give you any advice on how the Tiptronic compares to it.
Have you been driving in mostly 'S' (Sport) mode or in 'D' (Drive) mode? I have found that when driving in Sport mode, I can feel some of the shifts taking place. This is particularly noticeable when I'm slowing down to come to a complete stop and the transmission is downshifting. However, when I have the car in Drive mode, the shifts seem much more smooth and I don't really feel it shifting gears unless I'm driving the car aggressively. Since I've never experienced a Multitronic, I can't give you any advice on how the Tiptronic compares to it.