I got the IS-250, instead of the 350, just for the gas mileage (24/32). My go-fast days are behind me, but I wanted excellent braking and handling and the IS does that very well. For a 3700 pound car it feels very nimble.
I looked the the BMW330 first, but the IS won in the end due to the interior more than anything else. And I preferred the handling of the IS versus the BMW. Both cars feel like they are carved out of a brick. Very solid.
And the "start" engine button in the IS, is just flat out sexy. The only option I went for are the 18 inch wheels.