It seems to me that this car is Branded a Buick, rather then an Opel, because GM is hoping and believing that it will help start the rehabilatation of the Buick brand just as the CTS has improved the public perception of the Cadillac brand. While I Do not pretend to understand why GM felt that the Buick brand was better then Pontiac to grow on, once they made that decision and decided that the Buick brand would be positioned As the luxury brand between Chevrolet as the volume brand and Cadillac as ultimately the premium luxury brand, then a car like this was inevitable.
To say Buick will always be viewed as a Grandparents car is not looking at the long term history of cars. For example I had a friend who bought a brand spanking new 85 (ish) Hyundai Pony. A horrid little thing that wouldn't give heat in the winter because of its useless plastic heater core, had to have the carb beat on to get the choke to work when he needed to start it in the cold (something i got quit good at)and rotted away so quickly that when he hit a mail box at 35 mile an hour when it was 2 years old the insurance company wrote it off. Its problems weren't unique to that one car but infected all of them. If you could go back in time to 86 you would find that Hyundai was thought to be far worse then Lada, which at least would give you heat if you could get it to start. 25 years later Hyundai is considered one of the best brands and has been for a number of years. Buick is going to have to rebuild their image in the same way, by building cars that are much better (and more entertaining) then the previous models. That it can be done and perhaps even with in 8 to 10 years is reasonably achievable, in my mind, Given the history of Regal Grand Nationals and late sixty muscle cars they could use in advertising to high light a performance heritage if that was how they decided to position themselves . To me the only questions are if the new Regal will be good enough to move toward this goal and if GM has the where withal to take 10 years to rebuild the brand image.