I purchased a Lexus IS350 with fabric seats in 2008 autumn. I traded a 1992 Mercedes-Benz 260E for it. My IS350 has average fuel consumption of 23.5mpg, far better than that of 20.4mpg for the Mercedes 260E. The acceleration is very exhilarating, reaching 0-62mph times of 5.2sec, SS1/4miles is about 14.2sec (That's not far from the best data of 13.5sec, of an American media.). Namely, my IS350's level of performance is about the same level as that of the Mercedes E550,the BMW335i,and even a Maserati Quattroporte of 401 horsepower! Max speed of my Japanese version is electronically limited at 180km/h (112mph), but if the limiter removed, it has the potential of reaching 270-280km/h (170-175mph).
Bazooka power! It's as fast as the Jaguar XJR of 400 horsepower. The shock absorption of its suspension is very well suppressed; namely its ride is very supple. Fuel economy is on very high level considering its performance.
Back space is so-so, as wide as that of BMW 3-series. Mercedes C-Class offers much more rear legroom, IS's back space can be better. Skimpy luggage space. Not so good visibility.