I'm not suffering a second of buyer's remorse. The car is a kick to drive, it is loaded with features, and everything about is pleasing to the senses (I find myself just touching various surfaces and marveling at how perfect they all seem). It's tempting to think of the IS as a "budget Lexus". That may have been true of the 300, but this is genuinely a luxurious car--all Lexus. I'm getting about 32mpg on the highway and mid-20s around town. Much better than the new EPA ratings.
Hard to say. The car has so many great little features. Overall, I'd have to say the smooth and quiet ride, coupled with a genuine small-sports- car feel in maneuvering. The car just has everything going for it.
Maybe just one small easy-to-reach storage cubby for the driver. Just for my phone and my gate card.