Drove both RS3 and RS5 back to back today. I've driven the RS3 three times now, obviously first time for the RS5.
Very differend cars for different needs, the extremes in RS5 were much farther apart than in the RS3. While some of the appeal of the RS3 has worn off during just the three test drives, I don't think it would happen with the RS5 - for the simple reason that it felt so totally perfect for a daily. You can just drive it like any car, it's very comfy and refined, the seats are wonderful, and then if you are stupid enough to ask, it smashes your face off with a sledge hammer. The weight definitely feels, but in a totally different way than I would have anticipated. I think it's not a concern unless you go track it. For street use it's all fine. But when all that power catapults that weight into speed, that is simply brutal! I even got a slight headache after few strong accelerations. So there's way more reserve than you mostly need to use. The car feels fast even when driven quite calmly. So, don't hate it solely based on what's on the paper or how it performs in drag races.
There is room for improvement in the interior design and the virtual cockpit, but honestly I didn't mind them much during the test drive. As a negative I have to mention that there was some damn rattle in the back of the car. Maybe something you can fix, but these days I see red every time I hear a rattle in Audi, because it's way too common.