Overall, I like the new IS. It might be a bit overstyled, but at least it's unique. IMO, the F30 is boring. There is nothing really striking about it. It looks OK and appeals to a wider audience because it isn't a design that takes risks. That might be fine for some, but many buyers want something fresh and more aggressive. I think the IS hits on those points. My guess is the average age of F30 buyers has gone up from the previous generation. That's what happens when you make the 5 series more of a luxury car, then simulate that design on the 3 series.
I also think the ATS and C-class are better looking than the F30. The only car the F30 looks better than is the current A4. I'm also willing to bet the IS will drive better than the F30 since the GS already drives better than the F10.
Assuming they price the IS aggressively like they already do for the current generation, this will be a huge winner for Lexus.