This car is the best I've ever owned overall.
The only thing I would trade would be a BMW sport suspension, but it's not worth all the frustration I've had with my 535i ($20k more than the IS!).
I've had both the 250 and 350.
I stuck with the IS350 because I value the acceleration, but the IS250 is really great and sporty with good mileage.
The rear wheel drive platform has very precise steering with a firm suspension that still soaks up bumps pretty well.
If you like a cushy, quiet ride, go with the ES.
BMW, Acura, and Infiniti don't hold a candle to the overall combination of performance, reliability, and dealer experience.
There is no better service department than that of Lexus.
Direct/port mixed injection engine is powerful and efficient.
Ergonomics are unmatched--even by other Lexuses.
Styling makes my mother-in-law "drool", so she says.
The acceleration of this car is really more like 0-60 in 4.9s (see C&D), which makes it a real sleeper.
Infiniti G's are no match.
Lexus dealer service is bar-none the best.
Then again, I never owned a Bentley :-)
Stock suspension setup is better on the 250 than the 350.
The 350 has more understeer (Google it).
I installed the aftermarket F-Sport sway bars, which made the 350 handle great now.
Like ALL sporty cars, the aggressive wheel camber wears tires out much faster.
Probably 20k miles for a set of tires.