I comparison shopped/drove quite a bit before buying this car in June 2014.
Handling and the engine performance are superb--better than the E550 and 550i.
The interior may be a smidge behind the Germans in terms of fit/finish, but it is a minimal difference. The CUE system isn't intuitive, and I'd prefer just knobs and a straightforward information management system.
It took me about three days to feel like I had the hang of CUE. My car has the upgraded Kona wood interior, which is absolutely beautiful; I don't know that I'd pay for it, however, if not for the $6000 in incentives GM offered ($3000 rebate + $3000 "conquest" cash) and dealer's willingness to negotiate.
Suspension, handling, engine--no question GM hit a home run on these.
The CTS Vsport leads the class in these categories without question.
I know some people find the driver aids intrusive.
Things such as collision warnings, lane departure warnings, etc.
You can turn them off if you choose. I don't see anything wrong with these safety features.
CUE needs refinement. Just too many layers to get where you want to be in it. Oddly, I also noticed that the CUE screen's visibility diminishes quite a bit when I wear polarized sunglasses. Still doesn't offer some of the convenience features of Mercedes or BMW (e.g., self closing trunk lid). Not a concern for me--I wanted a great handling/performing car--but it is tough to compete with those manufacturers and charge similar prices without those features. Perhaps explains the substantial discounts GM offered in June.