The IS 350 is a very good alternative to the BMW 3-series. I was planning to get a 335i coupe, but gave the IS 350 a look and I liked the IS better than the bimmer. Dont get me wrong, the BMW handled real nice (free maintenance for 4 years is tough to beat), but I do most of my driving on the highway, so I needed that a car that has both comfort and performance. The IS also looks better than the BMW, and it was less noisy (dealership told me it was due to run flat tires).
The car is powerful, and very comfortable even with the sport suspension. Passenger-side standard 10-way power seats are a nice touch since its a option with the 3-series.
Fuel economy could be better. Even though you can manually turn the traction control off, it still comes back on after 15-20 mph.