The ATS is a pretty legitimate car from a drivers perspective. I am disappointed in the drivetrain options though, specifically the 2.0 Turbo. When I drove it I was not impressed with the power delivery. Reminded me a bit of what a turbo honda would be like....while that's a bit of an overstatement, the powerband felt narrow and peaky. My mazda has more downlow pull and both run out of steam quickly at high revs.
The V6 is a solid option but not nearly as strong as the 335i. I'm hoping the ATS-V will remedy this. The car overall is on par with the 3 series in terms of quality. I need to drive one again now that i"ve been in and driven a few F30's to compare things like road and wind noise.