Black/Flaxen Luxury- Very sharp. Like the Flaxen interior better in the IS than the GS for some reason. The wood is really nice as well.
Atomic Silver/Black base model- The Atomic Silver is off the charts IMO. It has a bronze tint to it but in no way comes off as gold (kiss of death). The color really has depth and splits the difference between Silver Lining and Nebula Gray. It is a really warm, interesting silver. The only shortcoming is that is isn't offered on the F-Sport.
White/Red F Sport- Love the red interior. Not the bright red like Infiniti and BMW use, but a more subdued red that you can live with everyday. I was also okay with the Nuluxe. It actually seems more grippy than leather for spirited driving. Also, my GS has Nuluxe in quite a few places so I guess I've gotten used to it.
I was impressed with the exterior of the IS, although unlike others have said IMO it didn't differ that much from the pics. It does have a nice stance. I also thought the interior was sharp, and the seats in all models fit like a glove. I think the interior looks upscale, modern and can compete with the best in class.
The F Sport was sitting in the delivery bay and was not driveable, so I will wait until things cool down a bit on the Lexus lots before I go back in for a test drive. I prefer a smaller car, and the IS still has good storage space with the fold-down rear seats. If it drives well, my GS may be sitting on the lot some time in the future. That is, unless a new coupe is announced.
One quick story... there was a guy in a Mercedes E Coupe at the dealership that asked me if that was my GS and how I liked it. Maybe we have another convert.